S3·E7 Scotch on the Rocks

Vicky finds an old claymore (a Scottish sword) in her attic. Lovejoy buys it at auction and is offered much more than it's worth for it. Puzzled, he investigates and finds the claymore is a map to buried treasure. Someone tries to steal it, so Lovejoy is not the only one hot on the trail. But the treasure is elusive - a supermarket has been built on top of it.