The action revolves around the new recruits of the Northern Ireland police, who are on probation under the supervision of experienced mentors before being allowed to enter real service. At the center of the plot is 40-year-old single mother Grace Ellis, a former social worker from England, who seeks to change her life, as well as the impulsive but clumsy Annie Conlon and shy Tommy Foster, whose shooting skills are lacking. Their work on the troubled streets of Belfast is fraught with great responsibility and regular dangers.