A former British Naval Officer now makes his living by smuggling goods around the Mediterranean. After being forced to dump his cargo after nearly being caught by the authorities in Malta, he is eager to recoup his losses. When a former colleague appears and tells a wild story about smuggling diamonds out of South West Africa, he sees his chance to make a lot of money....

Maggie Hobson (Patricia Routledge) decides to marry Willie Mossop (Michael Caine), the gifted but underpaid bootmaker in her father's shop. Despite Willie's objections, they marry and set up for themselves and, within just one year, take almost all of Henry Hobson's trade. Hobson (John Barrie), a heavy drinker, is told by his doctor that one of his daughters must return home to look after him but they all refuse apart from Maggie who, seeing her chance, agrees to help but on one condition: Willie is to take over the business, with Hobson relegated to the position of a sleeping partner with no say in the running of the shop.

South Africa in the 60s. The campaign of sabotage is halted and the arrests continue. The Special Branch obviously have inside Information.