Lisa has to choose who to save: Susan or Mandy? Chris learns new information that takes Lisa to a strange address, where she discovers incriminating information that someone tries to cover up. The killer calls later that evening for Lisa's decision.

The investigation is halted. David confronts Gardaí's top officials to expose Gill and Gough but finds no support. He reveals a long-hidden secret to his family. Lisa and Brennan follow a lead on the killer, investigating an abandoned slaughterhouse.