When you cross the line there's no going back.

Fifty Dead Men Walking (2008)

It's 1989, and in a Belfast torn apart by conflict and terrorism, petty criminal Marty McGartland is recruited by the British police to infiltrate the IRA. Guided by Special Forces officer 'Fergus', McGartland gains unparalleled insight into the organisation's dealings, providing his British handler with priceless, life-saving information. Based on a true story.