This is another colourful, action-packed Victorian detective novel about the exploits of agent Mary Quinn. At a young age, Mary Quinn is rescued from the gallows and taken to Miss Scrimshaw's Academy for Girls. The school turns out to be a front for a private detective agency. At age 17, Mary takes on her first case, A Spy in the House. In this, the second book of the series, Mary Quinn sets out to uncover the truth behind a suspicious death at St Stephen's Tower, better known as the clock tower of the Houses of Parliament. The accident occurred after hours in a highly public part of town and despite the presence of night watchmen. Mary, disguised as Mark Quinn, becomes a builder's assistant to find out the truth about the body at the tower.