In 1979, Britain’s MI-5 tasks the Directorate to deal with an issue in Belfast, Northern Ireland. MI-5 believes a rogue group, patterning itself after a disbanded British Army unit, is continuing that unit’s work, namely murdering IRA members and their families.

Mai wants this mission. One of the killers’ targets could be her cousin, Maigret Maitland McDiarmid, a new mother and Belfast’s Member of Parliament. Mai, still probationary after two long years, isn’t allowed to run ops on her own and has to wait for the availability of her partner, Alexei Bukharin.

Mai and Maigret have a positive reunion until Mai tells Maigret why she’s really in Belfast. She finally convinces Maigret the pending attack is real and overcomes Maigret’s distrust of anything English. Unknown to Mai, however, Maigret and one of the rogue group’s members have a connection, one that fuels a need for revenge.

Alexei’s and Mai’s team assemble at Maigret’s house, but using a relationship from Alexei’s past, the killers lure him away, leaving Mai, Maigret, and a Directorate operative known only as Fleming to confront the killers, led by an unconventional ex-soldier, Cari-Lee Felton.

On a rainy, summer night on a street in a Catholic area of Belfast, Mai and Felton face each other.

They both know only one will survive.