Candleshoe (1977 Norman Tokar)

The old pro Jodie Foster at her most winning playing fostered LA hard kid who agrees to scam an old lady thinking she's her grand daughter to find family treasure. Instead kid grows to like GM Helen Hayes, butler / chauffeur / gardener David Niven and his 'family' of adopted children. As baddies: Leo McKern and Vivian Pickles.

Adapted by a book from Michael Innes it's predictable but fun.