Discreet Inquiries: Ex Marks the Spot

In book 2, an ex-girlfriend of Richard's goes missing, and he's coerced by his best friend Jane - a cop and the current partner of the missing woman - to find her. Along the way he discovers a secret life she's been leading and dark corners of society she's been probing. Richard's investigative efforts lead to various attempts on his life, as he works on finding both the missing woman and his would-be killers.