While sailing lawfully up the Yangste in 1949, the British warship Amethyst found its return to the open sea blocked by Communist Chinese shore batteries that unexpectedly opened fire. In charge, Lietenant Commander Kerans was not however prepared for his crew and his ship to remain as a hostage for the Chinese to use as an international pawn.
American scientist Dr. Frank Smith is brought to Britain to help the C.I.A. There is a defecting East block scientist they want him to debrief. The commies are less than amused and set Dr. Smith up for a murder.
An Inshore Minesweeping Unit has been forgotten by the Navy after World War II on the peaceful island of Boonsley and they have adapted to their circumstances. The men still wear uniforms and the proper reports are filed, although the reports of hundreds of mines are exaggerated. The captain spends his time fishing, the Number One is busy romancing the only Wren on the island and The Chief Boatswain runs a wine smuggling business. Unfortunately the Navy start to get suspicious.
