1974. Nick and Rosemary Storey are seconded to the EU as national experts in an anti-fraud unit. At an EEC-Soviet conference, a Latvian Customs official seeks EEC help to tackle heroin smuggling from Soviet Central Asia through Riga. After an unsuccessful search in Tilbury, Nick and Rosemary, while visiting Rotterdam Customs, encourage them to search another Soviet ship. After a package of heroin is dropped covertly off the side, surveillance picks up a Turkish immigrant, who leads the authorities to a complicated network of Soviet organisations involved in unofficial heroin smuggling. As this is unwound, Nick and Rosemary have to make a perilous visit to Riga to extricate the ringleader. "Along the Watchtower" is the fourth published book in a series of detective stories set in Customs & Excise by Richard Hernaman Allen, a former Commissioner.