Robbie's first day in the armed response unit turns into a baptism of fire as Tony and Banjo find out what he's made of. Miller decides to give Liz his full support, but an unexpected invitation from the deputy mayor leaves her with serious questions about her boss. Meanwhile, Davina and Clarkey consider taking their relationship to the next level, which would mean coming clean to their partners, and a bomb threat at the Thameside Exhibition Centre leads to tragedy.