Catch up with Line of Duty episode 4 via BBC iPlayer for the next 30 days.

Fresh testimony launches AC-12 back on the trail of the Caddy, a corrupt officer with links to organised crime. But new disturbing evidence suggests the Caddy may reside within AC-12.

Episode 5 airs Thursday 21 April at 9PM on BBC Two. Get a sneak peek.

Episode one
Episode two
Episode three