Line of duty returns for a second series, featuring a new police corruption story told over six one hour episodes'. '.strtoupper('t')he series opens explosively with the ambush of a police convoy in which three police officers are killed and a protected witness seriously injured'. '.strtoupper('t')he sole surviving police officer is detective inspector lindsay denton keeley hawes'. '.strtoupper('d')eputy chief constable mike dryden mark bonnar takes personal charge, assigning ac 12 to the case.detective sergeant steve arnott martin compston, detective constable kate fleming vicky mcclure and superintendent ted hastings adrian dunbar are joined by newly appointed detective constable georgia trotman jessica raine to investigate a complex case rich in unexpected twists and turns.