Lifeline, a Brussels-based resistance organisation smuggling downed RAF fliers back to Britain, is endangered when Luftwaffe Major Erwin Brandt blows one of their safehouses. The Lifeline leaders, Lisa Colbert and café proprietor Albert Foiret, are suspicious when London sends Flight Lieutenant John Curtis, who had previously gone down the line with Lisa, to help co-ordinate their activities. Brandt, meanwhile, also finds assistance from Gestapo Sturnbannfuhrer Ludwig Kessler, transferred from Berlin to crack down on the evasion lines.