An anonymous email is sent to the CIA website: a scientist deep within Iran's nuclear programme is ready to talk. Harry Pappas, head of the Agency's Iran desk, knows that if the contact is real, he's looking at the intelligence coup of the decade.

With war imminent if he doesn't succeed, he contacts an old friend in MI6. Together they plan to identify the source and extract him from Iran for debriefing. For the job they turn to the Increment, a top secret and lethal black ops unit recruited from within the SAS. Their mission: to enter one of the most dangerous places in the world, Iran's heavily-protected covert nuclear facility.