The HMS Wagtail is a river gunboat, a ship seemingly at the end of her
unusual life, lying in a Hong Kong dockyard awaiting her last summons to
the breakers' yard. Commander Justin Rolfe is also seemingly at the end
of his useful naval life, an embittered man, brooding and angry from a
court-martial verdict. Then the offshore island of Santu is threatened
with invasion from the Chinese mainland.
The small British community must be brought out, and Commander Rolfe and
the Wagtail are ordered to the island....