The Brewer's Daughter

Sid falls for Grace Fitzgerald, the married heiress to a brewery, and is her alibi when Mallory arrests her for murdering her father in a fire. Fitzgerald, refusing to use Sid as an alibi, asks Father Brown to search for the real killer and he uncovers evidence that Fitzgerald's husband and her younger sister killed the father. The suicide and a note left by another lover of Fitzgerald complicates the issue as he had been sacked by her husband when he caught them kissing.