In July 1945 MI6 agent Paul Dark took part in a top secret mission to hunt down and execute Nazi war criminals Now it's 1969 and a KGB colonel called Slavin has walked into the High Commission with information which indicates that there is a double agent within MI6 Dark has been largely above suspicion during MI6's years of self-recrimination but this time he's in the frame For some it would be fight or flight time But perhaps the option is both fight and flight - whatever the consequences