Crisis Four is Andy McNab's fourth book and his second work of fiction, but he has already established himself as a brand name. His trademark is the SAS and dirty operations, so it will come as no surprise to anyone that the hero, Nick Stone, is a hard but fair ex-SAS man, now working for £250 per day as a freelance agent for British Intelligence on undercover missions which will be denied if they go wrong. The basic story is relatively straightforward. Stone undertook a mission to Afghanistan in the late 80s with a mysterious femme fatale, the posh Sarah; they had a fling and she promptly dumped him on her return. In 1995, they meet up briefly on another undercover mission to Syria which starts to go horribly wrong as Sarah appears to be working to a different briefing. Then, in 1998, Stone gets a summons on his pager to meet his bosses at Gatwick. Sarah has gone AWOL from her apartment in Washington DC and Stone's job is to find her. This he ingeniously achieves quite quickly and there then follows a long, tense chase across the US. Sarah's true past, and the secret that she holds, is gradually revealed and the ending is truly gripping.