Suspect: Season 2, Episode 3

2 - 3: Louisa

Susannah tracks down her ex-client, officer Louisa, who though initially hostile eventually opens up about a witness who saw her friend being killed by a man matching Jon's description. Louisa admits that she was threatened into silence and Susannah realises they might both be in imminent danger. Louisa sends Susannah a photo of the witness who she needs to find. As Susannah hurries away, it's clear that she too could now be a target.