Probing what could be a random street shooting, DI Glaspie turns to the victim's frightened family for clues. A key witness withholds evidence.
Glaspie and Bilk uncover a promising lead while MI5 gets involved. Under political pressure, David reveals Linh's secrets. Shaw endures a fresh trauma.
After another murder, Glaspie uncovers a deeper conspiracy. Karen spins out of control. Jane faces a reckoning. An informant begs MI5 for protection.
Glaspie closes in on the conspirators, Jane confronts a wrenching choice, David gets raked over the political coals, and Shaw makes a dire decision.