The Wrong One (The London Star Elite's Pickpocketing Investigation #3)
Rebecca King

When the finger of suspicion falls upon the occupants of the village's only lodging house, Marcus becomes their newest resident in his quest to find out if the landlady's brother, Ben, is working for Sayers. However, Marcus quickly finds it difficult to investigate each of the lodging house's rather eccentric residents, not only because he's distracted by Jess, his delightful landlady, but because it quickly becomes evident that it's not just Ben who's keeping secrets.