Part of the Isle of Man Film Series.
"Island at War" was a series of six episodes shown on ITV in July 2004. The story was set in the fictitious Channel Island of St.Gregory's, during the German occupation in the Second World War.
Much of the filming was undertaken on the Isle of Man, with the main square of Castletown featuring heavily.
See also the Isle of Man Guide.
Another notable recent film "I Capture the Castle" featured Castle Rushen as a location.
The cache should be easy to locate, but you'll have to take care not to be spotted by muggles as it's in a very busy area. The container is quite a bit smaller than the traditional film canister, but is fully equipped with a log book and pencil. If you're wanting to swap that giant-size teddy bear you won at the fair, however, this is probably not the cache to try.
Just behind the cache is the superb Castle Rushen, originally built about 1200 and the last stronghold of the Norse Kings of Man. Nearby are plenty of places of interest, including the old House of Keys, the old Grammar School, and the Nautical Museum (ask for a guided tour). The harbour area is well worth visiting, and the Glue Pot and George provide refreshment. The Tapas bar adjacent to the cache is excellent if you can get a table.
The walk out to Scarlett is an easy and very enjoyable stroll from here.