Expo Lana Washington is giving a routine talk, having just returned from secondment, when an explosion rocks the heart of the city. But is she ready to return to active duty?

The police launch an investigation to find the bombers, whose skill and sophistication keeps them one step ahead. Under pressure to get results, Helen makes a breakthrough.

As the team mourns Thom's death, a new lead emerges - an informant, promising intelligence on the terror cell. Meanwhile a journalist is sent a suspicious package.

Alex contacts the police with critical information about a new attack planned for that day, but Commander Francis warns the team against placing too much trust in him.

Lana breaks protocol to try to help Alex, knowing he has nobody else to turn to. Then the team makes a shock discovery about the terror cell they’re tracking down.