The Secret Tunnel (1948)

Storyline Roger Henderson, the young son of a wealthy British gentleman, lives in one of those grand British country estates surrounded by huge gardens. When a Rembrandt painting is stolen from the vault in the basement of the mansion, Roger and John Wilson (young son of the butler) discover a secret tunnel leading from the vault to another building on the estate. They then set out on a dangerous mission to bring the smugglers to justice.