While investigating the events on Sheena Island, Ark presented himself as Vincent Goldman in order to obtain information from Andy Holland. This was easy to do, due to Vincent never personally showing himself to Andy, but this had the unfortunate side effect of making Andy a vehement enemy of Ark's.
Vincent, once he learned of Ark's deception from Lott Klein, caught up with the detective, bent on killing him, but Ark escaped to the roof, Goldman getting possession of his dog tags in the conflict. He finds a helicopter there and takes off; Vincent grabs a hold of one of the railings and damages the fuselage enough to cause it to crash.
Ark survives the crash, but is left amnesiac in the process. Armed with a handgun, he travels back into the island's city, trying to explain what happened to him, finding an unconscious Vincent in a street, clutching the dog tags. This leads him to assume that the man on the ground is Ark. He finds the city overrun with zombies, using his gun to defend himself, but he presses on to discover the truth.
A phone call from Andy, coupled with photographs at Andy's workplace, convince Ark that he is really Vincent and thereby responsible for the horrible acts performed on the island. He also finds fellow survivors, Lott and Lily Klein, who both know the truth of his identity but refuse to trust him due to his fear to be "punished" by him for telling Vincent that he was a spy. He protects both children from the island's zombies, Tyrants and other creatures at numerous points, finally convincing Lott to confide in Ark about his identity. Ark's memories surge back, and he recalls his mission to put the Umbrella facility out of commission.
Ark and the Klein children locate an emergency helicopter in the facility, but a prototype for a new kind of Tyrant, named the Hypnos-T Type, stands between them. He manages to hold the beast off before joining the children in the helicopter, with the Hypnos-T Type in hot pursuit. Flying above the island, they discover the Tyrant managed to grasp onto the helicopter, attempting to kill the three inside. Ark then uses the chopper's missile launchers to finally obliterate the Tyrant, and he, Lott and Lily fly back towards the mainland.
Further notes Edit
In the game, Vincent Goldman grabs Ark's dog tags, but it is left unexplained why he would have dog tags, since he's a detective, although it is possible he is a former military man and simply kept his dog tags as a memento from his service. This, along with the fact Ark was able to successfully pilot an assault helicopter at the end of the game, suggests that he may have been attached to an Army aviation unit In his military career prior to 1998.