He's known to his employers as Number Four because he operates by four concrete rules at all times. He's known by this reputation because he's the clean-up man, just like the fourth batter in a baseball lineup.

He is the clean-up man of the contract killing world. If a contract goes awry, a target gets away, or somebody is seen, he's the man called to control the situation. Ruthless, efficient and believed by some to be little more than a myth, Number Four is the kind of man nobody ever wants to have to use twice.

Ten years before Theo Mavetti, head of an independent crime syndicate in Boston employed Number Four. Trying to save a few dollars, Mavetti crossed Four and very nearly lost his family for it. Now a new situation has presented itself, and as it begins to close in on Mavetti and his way of life, he has no choice but to make the call.

As high ranking officials and public personas begin turning up the victims of perfect crimes, the Boston Police press harder and harder on the case. Dern Beckett, an intense and rugged man from the mountains of Wyoming, leads the investigation and begins unraveling the connections that reach from offices on Capital Hill to billion dollar industries to the most prestigious academic institutions in the world.