Callum assures his colleagues that he will find the bomber, then a message comes telling them that another
device will explode in three hours. Grace interviews Carl Adams and Jeff Bowman - who were targeted in
the earlier attacks - but the team are shocked to discover that Emma\'s murderer has been in the station the
whole time. The bomb is traced to a mother on the school run. Mickey manages to drag her to safety, but
when Callum goes to save her baby, the car explodes.