"If you defeat multiple enemies in a row, you'll get yourself a nice bonus!" — Stone to the player via radio in The Mercenaries mode
Josh Stone (ジョッシュ・ストーン?) is a member of the Bioterrorism Security Assessment Alliance's (BSAA) West Africa division, although upon further inspection, Stone was the Captain of the first team Sheva Alomar joined with the BSAA and trained Alomar for eight months. After the training was complete, Alomar and Stone developed an extremely close relationship in which he refers to Alomar as "the little sister of the team".
Stone first appears at the crash site of the downed helicopter flown by Kirk Mathison. Stone and his team help Chris Redfield and Alomar as the two are being overrun by Majini. Redfield, Alomar, and Stone reunite at the train yard. Stone and Redfield introduce themselves and Redfield is surprised to see that Stone and Alomar already know each other. Alomar tells Redfield that she trained under Stone, and that Stone thinks of Alomar as a little sister. Stone then hands Redfield a PDA that has information on it. Some containing a picture of Redfield' former partner Jill Valentine. Stone then exits the room, and later on is attacked by a B.O.W. that was released by Excella Gionne.
Stone runs into Redfield and Alomar at the Oil Refinery alone after his team was wiped out. Stone and Alomar have a brief moment, and Stone then asks the two why they didn't retreat. Redfield states that he is here more on personal terms rather than the mission, and Alomar explains the situation about Valentine. The trio are then attacked by Majini, fighting off relentless waves of them. Stone unlocks the elevator and they make it up to a higher level. Stone then unlocks another door, which leads to their safety. At this point, Stone leaves Redfield and Alomar behind. As the oil refinery is about to explode due to Ricardo Irving. Stone rescues Redfield and Alomar in a speedboat moments before the oil refinery finally explodes. The team make it just out of reach from the explosion, and they decide that it's time to stop Irving once and for all.
Stone, Redfield, and Alomar are floating in the boat until Majini in speed boats come and attack them. The team are shot at and Redfield and Alomar take them out as Stone drives them out of danger. Through the mist, Irving's boat comes out of nowhere and Stone slams into the side of his boat by mistake. Redfield and Alomar take out the Majini shooting at them from the boat and then they get on board. Irving mutates, thanks to a sample Valentine gave to him. Stone then leaves the area under Redfield' orders. After Irving is defeated, he reveals to Redfield that all of the answers he wants awaits him in the caves. Stone takes Redfield and Alomar to the caves and then retreats to headquarters. He then went back and followed Redfield and Alomar, although they didn't realize that.
Stone enters the Monarch Room just missing Redfield and Alomar, the two he came back for. As he heads up the stairs he notices a woman passed out. As he wakes the woman, he realizes that she is the one and only Jill Valentine. He helps her up and he reveals to her that he is looking for Redfield and Alomar. Valentine tells him that they just went after Albert Wesker, and that he is aboard a tanker. Stone tells Valentine that he has a helicopter waiting and he is going after Alomar. He agrees to take Valentine along, after flirting a little with her, and the two leave the room. Valentine tells Stone that she had to go to the communication facility in order to tell Redfield how to defeat Wesker. Throughout their journey, the two are attacked by waves and waves of Majini. Stone and Valentine use the Majinis' weapons to their advantage, seeing as if it is the only way to escape. Once they reach the facility, Valentine contacts Redfield, with Stone's help, and she tells him that an overdose should do the trick. The radio is cut and Stone and Valentine exit to the rooftop. Doug, the BSAA agent who has the helicopter, has not reached the rooftop yet. Stone and Valentine are forced to fight off Majini until Doug finally arrives. Once there, Valentine is blown back by a blast from a rocket launcher. Stone helps Valentine to the helicopter and notices Doug is not aboard yet. Doug is then killed by the same man who tried to kill Valentine. Valentine holds off other Majini along with Killing the Majini with the RPG. Stone flies the two out of the area, and they both agree to help Redfield and Alomar with their fight against Wesker.
They then head to the volcano site where Redfield and Alomar are engaging Wesker. After Wesker lose his balance and tumbles into the magma, the pair helps Redfield and Alomar board onto the helicopter. But in a last ditch attempt, Wesker launches his mutated tentacle briefly snagging and destabilize the helicopter as Josh struggles to keep it afloat. After Wesker is killed by the combining effort of Redfield and Alomar, Josh takes the survivors back to shore, flying into the sunset