Detective Colette Cunningham takes a call from Dublin, where she has been named next of kin to her murdered daughter Kate, who vanished 20 years prior.

Surprised by her latest find, Colette travels to the hospital where Stacey worked to speak with those who knew her, in the hopes of understanding her daughter.

After a tense confrontation, Colette becomes convinced that Stacey was murdered, but she still needs evidence to prove it her suspicions.

After a visit from organised crime, Collette is more suspicious than ever about Stacey's supposed suicide and pieces together clues that point to a culprit.

Colette follows up on a case that leads her into contact with someone who knew Stacey, which results in a new lead - Stacey's last call.

With a suspect in her sights, Colette closes in on the truth; with Patrick and Siobhán's help, Colette finally discovers corroborating evidence.