Clark Kent is interviewed by Peter Kirby, a young journalist, who is curious to find out the connection between Superman and the contract killer named Tommy Monaghan, also known as Hitman. Kirby is writing a book on Gotham City crime figures for a now defunct publisher and happened to came to Noonan’s Bar, where he became aware of Tommy’s relationship with Superman when he saw an autographed picture of the Man of Steel. Kirby asks Clark point blank how Tommy ended up with Superman’s autograph, which Kent reveals that Superman did indeed gave Tommy the autograph after a meeting by chance. Clark then reveal a story of what happened some years before when the Justice League of America were based at the Watchtower on the moon in which he request that Kirby doesn’t use or repeat this to anyone.
Years ago, Green Lantern leaves the Watchtower to investigate a damaged space probe that NASA has lost contact with. Scanning the probe with his ring and sending the results back to the tower alerts Batman to a potential threat.
Tommy, meanwhile, is in Gotham following a tip-off that four killers are after him. As the killers argue about who is better qualified to kill Monaghan, Tommy throws a bomb into the room, killing all of them.
At the Watchtower, Batman reveals what was identified by Green Lantern’s ring once he returns. The Bloodline parasites appear to be on the space probe. Realising they need a survivor of the parasites’ earlier attack, Batman heads down to Gotham where he finds Tommy and brings him back to the moon. Green Lantern is embarrassed when Tommy recognises him and tells the other League members (Wonder Woman and Flash) of how they had teamed up, causing Batman to lecture Lantern on the morality of associating with a hired killer. His tirade is cut short when Superman walks in and also recognises Tommy, greeting him as a friend. Batman tells Superman of Tommy’s profession which he shamefacedly admits to.
Tommy’s blood is tested and compared to the readings from the probe; the creatures on the probe appear more advanced and a greater threat. The League disagree on how to deal with the threat of the aliens but their hand is forced when the probe accelerates and heads for the moon; it crash lands and Superman flies out to find any survivors.
At the Watchtower, the four remaining heroes and Tommy suddenly feel their individual powers waning and it is Tommy who reminds them that if it has happened to all of them, it may have happened to Superman, who is outside on the moon’s surface.