During the team's search for the killer, Jack works alongside an old friend from Northern Ireland, a fearless journalist who has dedicated her life to exposing the suspected organisation. As the team investigate further, they realise they have uncovered a complex conflict sustained by ties of loyalty, family and retribution.

When Thomas sides against her findings on a controversial case, Nikki suspects foul play and takes steps to prove her theory. Jack and Clarissa follow a forensic trail connecting a dead researcher with a billionaire scientist and a secret testing programme.