The Adventures of Black Beauty (1972)

S1E25 The Barge

Vicky and Beauty strike up a friendship with Maggie, an older woman residing by the river, whose son has recently been released from prison. When a string of valuable art thefts takes place, Vicky uncovers the stolen paintings hidden on Maggie's houseboat. With Albert and his mother in a precarious situation, Vicky, along with her friends and her horse, embarks on a quest to uncover the truth.