Disaster strikes the gang as a drug mixing factory is busted by the gardai. John Boy blames Stumpy who he believes sold them out. Darren, desperate to get out of the game, robs an ATM machine and makes a downpayment to John Boy against the debt he owes. John Boy, however, wants Stumpy taken care of and he wants Darren to be the one to deal with it.

When a container of drugs is busted at the docks, John Boy decides to double cross Fran on their deal. Fran retaliates against John Boy. John Boy is furious and orders Nidge to pipe bomb Fran's house leaving Fran determined that the escalating gang war will not end until he has revenge.

The crew are in festive spirits as Trish has the baby on Christmas Eve, while Rosie has come back to Dublin and Darren falls in love with her all over again. However the gang war is still raging, and John Boy orders Tommy – already caught between his friendship with Debbie and his worries about Siobhan’s money runs – to kill Fran. The hit goes wrong, and someone else becomes fatally caught up in the aftermath.

As tensions come to a head the gang threatens to implode: Luke's obsession with Mary is becoming more dangerous, while Siobhan's panic attack at the airport could get Tommy killed. Paranoid John Boy finally tips over the edge of sanity when he finds Debbie taking heroin.

Nidge swiftly fills the power vacuum and gets the gang back to business as usual. Rosie has realised what her lover has become, and Darren is devastated when she breaks up with him. Meanwhile Mary finally realises the extent of Luke's psychosis as she finds him lurking in her bedroom at night.