 Once outside, a Psiren begins to overpower him with a powerful illusion, but is killed by a second Psiren disguised as Kryten, whom Lister promptly kills when it calls him "Dave", something the real Kryten would never do.Managing to get back aboard, the others find that a third Psiren has disguised itself as Lister, leaving them unable to determine who is the real one and forced to hold both at gunpoint.To determine which one is false, the crew ask them to play guitar, and shoot the fake when it plays well, knowing the real Lister is terrible despite his belief that he is excellent, determining the Psiren's illusion was based on this belief that his genuine skill set.