Sometime before the events of Sonido de Tortuga, she met Claire Redfield and Inéz Diaco when they were giving a lecture about threats coming from B.O.W.s in her high school and they keep in contact with each other since then.
She first appeared alongside Inéz, who she thought might have the information about the mutant fish that Claire had encountered beforehand, Marilou then thanked Inéz for arriving at the island. She quickly notices the filming and berates the film crew for filming in their village without their permission first. She ended up in a brief scuffle with the show's producer Mike D. Seaman, who assures Brown Anderson that he can obtain it from the island's officials, Seaman ended up pushes Marilou out of the way, Inéz quickly catches her and nearly punches Seaman. Inéz then informs him that she is part of Terrasave, who is sent to investigate the area. Their presence ended up making Seaman worry as they are usually are an indicator of bioterrorism.
After the scuffle, Inéz and Marilou explored deep into the island and come across a large, ruined stone building. Marilou explains that this place is usually used as a temple by shamans in the area.
While exploring the temple, Inéz notices something suspicious about one of the objects in the room. After removing the drapes with Marilou, they find behind it abound, four-armed, masked being with various tubes. Inéz then deduces that the creature was a B.O.W., confusing Marilou, who does not know was a "B.O.W." is. Inéz then explains to Marilou the history of B.O.W.s, mentioning Umbrella, infamous for making the "Tyrant" and "Hunter models". Inéz prepares to take a photograph of the creature to send to Claire, but the two are ambushed by attacking villagers and Inéz drops her phone. The village shaman from earlier appears behind and takes Marilou hostage, threatening to cut her head off. Inéz is forced to the ground and her handgun and phone are confiscated. The shaman explains to Marilou that the creature is not a monster, but her "husband". The two are then knocked unconscious and tied-up. They are later then found by Seaman and an idol survival contestant named Zǐlì.
After the B.O.W. has come to life and kills Seaman by slicing him in half, Inéz unravels herself tries to wake up Marilou, Hearing her TerraSave-issue phone ringtone, she rushes to it and turns on the 'SOS' and 'Track Me' features, which allow other TerraSave members to work out her location. When the creature swings at her, Inéz drops the phone and it smashes on the floor. This worries her, as it is possible the signal was not received by Claire.
Inéz raises her handgun at the creature in the temple. Marilou is awake but still on the floor. Inéz calls out to her, warning her to run, and begins firing at the creature's propeller blades in an effort to break them. Inéz shoots at the creature in the temple, which pushes its fans ever closer to her. Shooting has little effect, as the rotors deflect every bullet. Instead, Inéz changes tactics to distraction and shoots at overhanging fabrics which collapse onto the creature, giving Inéz and Marilou enough time to run out into the jungle.
After the crewmen, the contestants were either killed or infected. Out at the ruins, Diaco inquires as to their origin. Mabou tells her the American built up a military base on the island over eighty years ago (before 1934). Marilou starts to wonder who the B.O.W. was she encountered in the ruins earlier that night is, recalling that her fiancé Lopez and her brother disappeared recently, and the Shaman referred to the B.O.W. as Marilou's husband. The conversation is cut off when the B.O.W. returns. Diaco is out of ammunition and is forced to challenge the B.O.W. to a fight while avoiding the propeller blades fixed to its arms. Diaco runs in between the B.O.W.'s blades and jumps on top of it. She stabs it through the back of the head and jumps off. The B.O.W. changes tactics - rather than aiming the propellers at both Diaco and Mabou, it has turned all its attention to Diaco. As the blades approach her and she drops her knife, Mabou is able to pick it up and stab the B.O.W. She calls for Diaco to run, ready to sacrifice herself to the B.O.W., but it is shot by the BSAA helicopter before it can do so.
Diaco and Mabou look up to see a second BSAA helicopter fly over, with soldiers dropping down by a pe from one as the second, identified as "Hawk 2", provides fire support in distracting the B.O.W. The B.O.W. exhibits remarkable jumping ability and comes close to destroying the helicopter. Claire checks up on Diaco, who suffered a deep cut in her left arm by the blade and gives her more ammunition. The B.O.W. finally succeeds in hitting the helicopter, and its crew descends the rope as it begins spinning out of control. The same happens to Hawk 1.
After the battle between the BSAA and Morio and the sudden appearance of Schraube Dämon, Captain Parker Luciani hands Claire the map of the island and orders her to take the civilians away, she realizes Marilou is absent. Mabou has already run away but finds that Morio has caught up when she falls. Morio is suddenly unable to kill her, giving Parker time to shoot it. Takeru Tominaga picks her up and takes away with the other survivors, As he and Mabou flee from the combat zone, Tominaga takes a shotgun and some grenades from one of the dead BSAA soldiers, he hands the survivors with weapons.
As they are led by Redfield to an apparent safe house, Redfield and the others reach the ruins of the apparent safe-house, which appears no different in condition from the US military base. Redfield presses a button on a control panel, and the entire floor of the room begins moving down like an elevator. She reveals that the safe-house is in fact an Umbrella laboratory complex. Based on information she has recently acquired from BSAA headquarters, Oswell E. Spencer had the facility built after the 1998 Raccoon City Destruction Incident.
The island survivors have reached the bottom of the elevator and are now exploring the Umbrella laboratory. Some are unfamiliar with the nature of the island. Claire explains that with the slow collapse of Umbrella after the Raccoon City Destruction Incident, Spencer founded the lab with the hopes of it developing a mutagenic virus that would make him immortal. Inéz suggests there may be anti-B.O.W. weaponry in the lab, and they split up into three groups with Marilou, Claire and Inéz partnered up.
Tominaga and Yuki Mayu trigger a door to open, which leads them to a large room containing culture tanks. In one of the tanks is a fully-grown Hunter. The two trigger an alarm, which wakes up the Hunter. Redfield's group finds themselves in an office, one of the desks had the same photo which Claire immediately identifies as Dr. Alex Wesker.
The three overhear the intruder alarm triggered by Tominaga and Yuki, Inéz is first to reach the culture tank room and raises her handgun at Hunter's face while Yuki; Tominaga, and Marilou keep away. Her shots repeatedly miss due to its agility. She narrowly avoids its claws, and the B.O.W. smashes into another culture tank. She manages to shoot the creature but receives a deep cut to her side. She holds off on firing until the Hunter, now calmer, walks within close-range. Marilou and the others have snuck back into the culture room while the Hunter approaches Inéz. They push a culture tank, intent on it falling on the Hunter. The glass smashes in the impact, and the Hunter is knocked out. The others arrive and try to tend to Diaco's wound, which is worse than she lets on. The Hunter begins to rise up and slashes its claw yet again. The force of the impact impales her with each of the three nails. Tominaga begins firing with the BSAA assault rifle he recovered and kills the creature, Inéz dies in Claire's hands with her promise to bring the survivors home and Marilou cries at her former friend's death
The Shaman speaks to the group on a tannoy from a room above them. Claire realizes the Shaman is the one pulling the strings behind the incident, and ultimately responsible for Inéz's death. The Shaman explains their being on the island. He served for the Kodoku Project, a research experiment to create the superior creature. Its name is inspired by the Kudoku, a Japanese folk magic spell involving insects being placed in a jar and forced to fight to the death. The staff interpreted that literally and created B.O.W.s that would fight each other until only the strongest is left. The mutant virus strains within the body of the survivor was then extracted, and an islander was infected with this virus to become the ultimate life form. This creature, dubbed Morio by Tominaga, was made to believe it must kill all strong people and to prevent escape, explaining its sabotage of White Castle. The Shaman took on his appearance in order to experiment on the island natives, who would accept the virus if thinking it had folk magic qualities. The lab was abandoned by design, as Dr. Wesker's extreme views of the survival of the fittest were also applied to the research team, with the Shaman the sole remaining scientist. Finally, the Shaman reveals his true identity as Dirk Miller. As he takes his mask off, Claire recognizes him as the man photographed with Dr. Wesker. He continues describing the events on the island to Claire Redfield. He reveals that other people beyond Mike D. Seaman have come to the island seeking its secrets, but all agents have been killed. The creature Morio is explained as retaining some of his human memories that surface occasionally. Morio was able to escape from the researchers into the jungle. Described as a failure, the researchers had to abduct a second individual to use as a B.O.W., explaining the Schraube Dämon's existence. As he is talking, the propeller-bladed B.O.W. enters the room
The Schraube Dämon singles out the girls as his targets, distracting him from Tominaga, who fires at him. As the Schraube Dämon turns to face Tominaga instead, a flash grenade is tossed at him. Temporarily blinded, he begins swinging his propeller around wildly. With the door sealed, the group's only chance of escape is via air ducts, but no one can reach it. It is agreed that Yuki Mayu; Marilou and Zǐlì will stay behind, while Tominaga; Claire Redfield, and model contestant Laura Bierce distract the Schraube Dämon. It is only when Marilou notices Zǐlì's absence do the group realizes her disappearance. The B.O.W. attacks, but Claire manages to jump into the vent by climbing onto it. Tominaga realizes that since the B.O.W. fights the strongest, it would naturally ignore the girls as only he has attacked it.
Claire managed to reach Miller's office and goes to his computer to open the door to the B.O.W. culture room, the others are ready to escape, but Bierce begins to suffer pains having been infected prior to the events. Morio enters the room in search of the Schraube Dämon, and the two begin fighting once more.
After Bierce takes off away from the others and Takeru leaves the two girls and gives chase, Yuki and Marilou head into Miller's office to meet back with Claire. The window observing the culture room cracks, caused by Morio being thrown into it in his fight with the Schraube Dämon. Ultimately, Morio succeeds in killing his foe, which the computer recognizes as him being the final specimen. The computer asks for one of the researchers with S-level security clearance to proceed to the next step of the experiment, at which point Dr. Miller falls out of a cabinet, having been garroted.
Claire looks over the body of Miller and when Zǐlì steps out, Marilou immediately notices the blood on her hands, Zǐlì shoots a hook out of her bracelet, which drags the handgun out of Redfield's hands. Throwing her to the floor before she can use her combat knife, Zǐlì raises Redfield's handgun to Yuki, forcing her to get in the corner. Zǐlì then drags Dr. Miller to the computer, revealing he is alive and had to be so so she could use its face scanner to verify his identity after the B.O.W. test. With the machinery preparing to extract the virus from Morio's body, Zǐlì has no further use for Dr. Miller and kills him.
As Morio is held down by the culture room's machinery for the virus extraction, Zǐlì begins taunting Claire and offers to explain what her mission was: she is a spy that was recently hired on behalf of Shenga-Ya Pharmaceuticals to locate "Umbrella's treasure", among the remains of Umbrella's massive research that has been left unclaimed by other bio-weapons manufacturers. Seaman had his own goals and wanted Zǐlì to help him, but was unaware she was a spy rather than an easily swayed actress. With the virus extraction complete, Zǐlì now has the sample in her hand, which she says is worth tens of millions of dollars. Tominaga arrived at the observation room to find Zǐlì taking hostages. She is able to run up to him and disarm his assault rifle. Claire tries to grab it but is kicked on the floor. They are then knocked unconscious by Zǐlì, who decided to torture them for information suspecting they may know more about the facility.
After the zombified Bierce bits Zǐlì and tackles both of them fall down to the pit, Yuki begins to untie Tominaga, seriously injured and bleeding out, Zǐlì injects herself with the virus sample. Looking down the pit, Claire takes notice of Zǐlì's mutation and she ushers everyone to run out and escape using Zǐlì's boat. The group escapes the facility with the guide of Marilou, they managed to reach the surface and arrived at the beach, where they witnessed mercenaries killing and stacking zombies on top of each other, the survivors are then captured by the mercenaries.
They are then surprised there really were uninfected survivors. Claire offers to negotiate their survival and passage in exchange for information on Zǐlì. The team leader is unwilling to negotiate with Redfield, either out of general refusal or belief her injury is an infection. Tominaga starts fighting with one mercenary as Yuki and Marilou are taken away to be interrogated instead. They do not shoot him for this infraction, as they are quickly distracted by the approach of a new mutant, Zǐlì, who claims the right to kill the survivors. Zǐlì begins jumping in the air to keep out of the mercenaries' vision, succeeding in severing one mercenary into chunks while he looks the wrong direction. A mercenary armed with a Debrainer is killed soon after. With the unit on the beach reduced to two, they call in the three reserve mercenaries from the boat, leaving it open for the civilians to escape.
After they armed themselves with weapons, Claire looks around for a way to start up the boat, the body of a barely-living, the dismembered mercenary is flung at them as Zǐlì makes her approach. She grabs Marilou first, who releases a scream so loud till the point Morio can hear them in the lab. As Zǐlì begins choking Marilou, Claire returns to get the rocket launcher, as Takeru Tominaga and Yuki Mayu move to the beach to shoot her. Yuki realizes they cannot use the rocket launcher without sacrificing Marilou, who Zǐlì announces her intention to rip to shreds. Morio arrives at the beach and begins fighting Zǐlì. The survivors now have a chance to rescue Mabou in the fight, but Redfield is too injured to rescue her. Tominaga elects to do the rescuing, with Redfield using the launcher.
Zǐlì has succeeded in grabbing Morio and hangs him in the air with Marilou. She removes his mask, Marilou shockingly realizes it's her own brother Eliseo Mabou. Tominaga charges at Zǐlì, firing the assault rifle and ducking her arms. When he is out of ammunition, he uses it to block the sharp spike at the end of one of her arms. He switches to a machete and continues charging, severing one of the arms. Zǐlì reacts in pain and drops Marilou. Tominaga and Marilou run away as Claire fires the rocket launcher hitting the two, with Marilou screams out for her brother and Yuki holding her back with tears. They are then seemingly died from the blast.
The pair of BSAA choppers arrive with one containing an injured Parker, who is the only one to have survived the skirmish between the two B.O.W.'s. Yuki and Tominaga then visit Marilou, telling her how her brother has managed to protect her and the others from harm's way with Marilou thanking them tearfully and Mayu hugging her for comfort. Claire, Parker, and Marilou are then taken away in the first chopper deemed to be injured and the first priority.
After the traumatic events of Sonido de Tortuga and following the loss of all her families and friends, Marilou Mabou has now lived with the aid of Terrasave, joining and becoming a member of the human-rights organization.
List of appearances
- BIOHAZARD heavenly island 1
- BIOHAZARD heavenly island 2
- BIOHAZARD heavenly island 3
- BIOHAZARD heavenly island 4
- BIOHAZARD heavenly island 5