Is Jim Gordon really a murderer? Batman #155 reveals the complicated truth behind the assassination of Gotham's mayor

November's Batman #154 ended with a helluva unexpected cliffhanger: the shock reveal that Jim Gordon was seemingly behind the murder of Mayor Nakano. The issue ended with a furious Batman beating up Gordon who had pulled a gun on him, only for the two to collapse in despair, their decades of friendship seemingly shattered.

Today's Batman #155 provides some fairly conclusive answers to the mystery surrounding Nakano's murder and Jim Gordon's murky recent past, while also inching the storyline about Bruce's possible secret brother William forward. It's a terrific issue in what's shaping up to be a really intriguing final story arc from Chip Zdarsky and Jorge Fornés.

Spoilers for Batman #155

Batman #155 opens with an extended flashback to 13 weeks prior. Gordon and Bullock's detective agency is working a routine infidelity case which turns out to have been filed by the mayor's wife, Koyuki. Gordon investigates but finds no evidence that Nakano is stepping out on her. When Jim meets Koyuki, however, the two form a close bond – one that quickly takes a turn for the unprofessional when Gordon saves her from some assassins. With emotions running high, the two embark on a passionate affair of their own.

Nakano eventually finds out about his wife's infidelity and punishes Gordon by having him replaced by Vandal Savage, leading to his eventual alliance with Bullock. Jim eventually confronts Nakano in a meeting that ends with the latter shot dead.

Gordon continues to plead his innocence, but his memories of the night are vague. Everything about these pages, from Jim's desperate dialogue, to the close ups of his tired face, and Batman's own certainly that the killer surely can't be his friend is working to sell us on the idea that Gordon's telling the truth. The only trouble is... he isn't. Batman investigates further and finds evidence that Gordon really is the killer.

There is, thankfully, an explanation for this alarming development. Gordon reveals to Batman that he barely remembers the events of the night in question, but he wanted Batman to investigate so that he would have a clear answer to what happened one way or another. Just as Vandal Savage's cops bust in to take the Dark Knight down, Batman realises that there's something amiss with Gordon's glasses. Studying them, he finds evidence of the Mad Hatter's mind control technology – clearly Jim has been used as an assassin without knowing it.

But why would Jervis Tetch want to take down Nakano? Bruce quickly puts two and two together and realises that the Hatter isn't behind all this, the Riddler is. He'd previously noticed that the design of the new NygmaTech logo awkwardly looked like there was an extra T in there, spelling out NygmaTetch – a clue designed to taunt Batman. And that's your cliffhanger.

Elsewhere in the issue the matter of Bruce's supposed long-lost brother William Pureford is also briefly addressed. It turns out that Leonid Kull (who we already know is a member of the Court of Owls) is representing him legally. Bruce approaches Leonid, but is roughed up by his bodyguards. Bruce takes a tumble, but uses it as a chance to sneak a tracker onto Kull's shoes. There's only two issues of Chip Zdarsky's run on the title left, and quite where this particular storyline is going is anyone's guess, but it sure feels like we're in for a gripping finale...

Batman #155 is out now from DC.

Here's everything you need to know about Batman's mysterious Court of Owls.