After Constable Nick of Aidensfield and Heartbeat fame's retirement, he helped create a small private police force of monk-constables serving Maddleskirk Abbey and its adjoining college. The body of an unknown man is discovered in a huge stone coffin in the crypt and Nick and DCS 'Nabber' Napier of the local constabulary welcome the assistance of the monk-constables or monkstables as they become known, as their knowledge of the abbey, its history, practices and personnel proves invaluable to the detectives. As the murder investigation hots up, a prominent pupil of the college goes missing and the monkstables find themselves pitched into an intense criminal investigation as they search for the missing boy. With help from retired Sgt Oscar Blaketon and ex-PC Alf Ventress, and some input from Claude Jeremiah Greengrass, Nick's experience is put to the test as a killer stalks the hushed corridors of Maddleskirk Abbey.