Sometimes the easiest jobs end up being the most complicated...

Viper's not back. At least, that's what Alina Maschik keeps saying. But when the head of MI6 requests her services, she agrees to a quick and simple job – plunging herself straight into trouble.

Michael O'Reilly has a problem. His cover is close to being blown by the two people who know him and Viper best. When terrorists threaten the largest oil refinery in Europe, he's more than ready to return to work—even if it means jumping into Viper's hot water.

From the Impressionist wing of the Philadelphia Art Museum to the streets of Rotterdam, the nation's most deadly operatives race to unravel the truth behind three notorious mercenaries—and a smuggling operation that's wreaking more havoc than anyone cares to admit.

Foreign agents, undead assassins, an invisible criminal cabal, and the Jersey mob? Who says retirement is boring?