Mike is dragged away from Jack's stag night by a terrified, yet unreliable, informant who's desperate to talk to Jack. Mike simply wants to stop him turning up at the reception, but when the informant turns up dead and Jack disappears, Mike finds himself being pulled into a dark underworld of which he knows nothing.

The squad investigate the attempted rape of a female barrister who it seems was apparently saved by a leech. They find that she has been attempting to have a child, and has been been impregnated in-vitro with her late husband's sperm, but the pregnancy is not normal.