Exit Strategy by Steve Hamilton

In this second book of the Nick Mason series, Nick is still indebted to criminal Darius Cole and is tasked with eliminating the witnesses who put Cole in prison. Cole figures if everyone who testified against him is dead, he will walk out of prison a free man, but both the authorities and the man Mason replaced as Cole's henchman are onto him. With Cole continuing to threaten to harm those Mason holds dear, will Mason switch sides?  While I really enjoyed the first book in the series, The Second Life of Nick Mason, this book's plot was slight and not as satisfying.