Two more adventures for the Baker Street sleuth. In 'The Mazarin Stone', Holmes (Jeremy Brett) is engaged by the Prime Minister to recover a stolen crown jewel. Watson (David Hardwicke), meanwhile, is investigating American John Garrideb, unaware that his case is linked to Holmes'. 'The Carboard Box' sees Holmes called in when a spinster is sent a package containing two severed ears. The police dismiss it as a sick prank, but Holmes is not so sure.