by Tony Williamson
Starring Ewen Solon
with James Grant, Callum Mill
Guest stars: Ralph Michael, Veronica Strong, Tom Criddle

Watertight security is a vital necessity for all customs and excise offices. The secrets contained in them concern huge sums of money - and can be worth equally large sums to anyone who can get hold of them. In this week's story Smith and Ross attack the problem from two sides, both with equal application.
(First shown on BBC-2)