Holmes Is Missing: Patterson's Most-Requested Sequel Ever (Holmes, Margaret & Poe #2) by James Patterson, Brian Sitts

Who do you call when the world's greatest detective goes missing? Detectives Poe and Marple are on the case to find their partner and make it out alive.

“Best-selling author James Patterson populates his murder-mystery novels with cold-blooded killers and smart detectives” (USA Today). In Holmes is Missing, PI Brendan Holmes has committed the perfect crime—he’s made himself disappear.
 
Success has come quickly to Holmes, Marple & Poe Investigations. The New York City agency led by three detectives—Brendan Holmes, “the brain,” Margaret Marple, “the eyes,” and Auguste Poe, the “muscle”—with famous names and mysterious pasts is one major case away from cementing its professional reputation. 
 
But as a series of child abductions tests the PIs’ legendary skills, the cerebral Holmes’s absence leaves a gaping hole in the agency roster.
  
Only by closing ranks and solving the mystery within can they recover all that’s been lost.