Irish Blood Finale Ending Explained: Declan Murphy's Killer Twist Changes Everything

Irish Blood finally answers its biggest question, and it does it in a way that is less whodunnit and more 'oh, that is messier than we thought.' The six-episode season saves the reveal for the finale, and the truth about Declan Murphy is not the tidy murder mystery the show kept teasing.

So... who killed Declan?

Una. Declan's own sister.

The show spends most of the season circling the same debate: did Declan fall by accident, or did someone push him? The finale lands on pushed, but not in a premeditated, moustache-twirling way. Fiona gets the full story straight from the person responsible, and it is ugly because it is human.

What actually happened on that cliff

Una tells Fiona she shoved Declan during a heated argument, not realizing how close he was to the edge. One bad moment, one bad push, and he went over. The fight kicked off because Declan wanted Una to serve as a witness in his investigation, and she pushed back — literally, with tragic results.

• The mystery payoff arrives in the finale of the six-episode season.
• Fiona hears the truth from Una herself.
• Declan was pushed off the cliff, but not as part of a calculated murder.
• The argument started over Declan pressing Una to be a witness in his investigation.
• Una shoved him without clocking how close he was to the drop.
• The Garda (Irish police) arrest Una for Declan's death in the closing stretch.

Where this leaves the show

Declan's case is finally closed, but the finale leaves plenty of other threads dangling. The town's past and present are still a knot, with more secrets clearly lurking. If the series comes back, that is where the story feels headed — deeper into all the stuff beyond the cliff.