Thing Thing 3 starts off as Project 154 contacts an anonymous person, during the conversation the anonymous person is explaining to Project 154 that he (?) knows he was a bio-weapon created by Systems Corp., and how he defeated Poseidon and Zeus (System Corp.'s most powerful machines in the game so far) and he tells Project 154 some instructions about a card in Sunset City Project 154 still doesn't know what is going on and the mysterious person doesn't tell. After being dropped into Sunset City he is attacked by the mercinaries from Systems Corps, after defeating them and finding the card he exits Sunset City and meets the person, who is, in fact, Project 153, who was sent to kill him. After defeating him(?), he(?) sends 154 down to a frozen underpath tunnel. 154 fights his way to the end, which turns out to be Systems Corp. 154 fights his way to a containment chamber. 153 tells him that he(?) might not be able to kill him, but he(?) knows someone who stands a good chance. 153 sends Vahl Dreig after him, and 154 kills the monster. 153 then says that he(?) always plans ahead, and 154 is trapped in the containment chamber.

End of Part 3.