The missing piece (#1) : Jigsaw Files
(Book)

PI Charlie Dodge knows what it's like to have something important disappear. His wife, Annie, suffers from early-onset Alzheimer's, causing her to remember little of the life she shared with her husband. Charlie has devoted his career to saving what he can--missing people, threatened lives. But when prominent Denver multimillionaire Carter Dunleavy vanishes without a trace, Charlie and his assistant, Wyrick, discover missing doesn't always mean gone. It turns out Carter didn't vanish after all--he's gone into hiding. Someone in his inner circle wants him dead and now Carter needs Charlie to expose the culprit before the Dunleavy empire spirals into ruin. But with a tangled web of suspects looking to silence Charlie's investigation, he'll have to find Carter's would-be killer and fast, before the traitor can finish the job.