Sherlock Holmes faces a sinister case risking friends' lives. American Amelia joins, seeking her father after her mother's murder. Despite differences, they solve a conspiracy and her mother's case.

Based on actual events that took place on 26 April 1974, former debutante turned IRA member Rose Dugdale and three comrades carried out an armed raid on Russborough House, Wicklow, in which nineteen masterpieces were stolen in an effort to support the IRA’s armed struggle. The film plays out over the course of the days following the raid, when Rose is in hiding in a remote cottage.