When wealthy recluse Henry Bernard is taken ill with food poisoning, his estranged son Philip flies in from London, voicing concern that Lisa, the faithful housekeeper, tried to kill him, though Jim is not convinced. Henry later dies, due to a supposedly accidental gas leak, leaving everything to Lisa, strengthening Philip's accusations. Lisa is duly arrested but she has been keeping a secret for many years, which changes everything and leads to the apprehension of the real killer.
—don @ minifie-1