Maggie’s Secret is one of those TV movies that nearly fail by being so successful. That is to say, this hour-long drama about the child of alcoholic parents is so convincingly done that it’s almost unwatchably depressing.

Fifteen-year-old Maggie (Joanne Vannicola) holds her family together: Both her mother (Mimi Kuzyk) and her father (Joseph Bottoms) drink excessively, and Maggie ends up running the household and overseeing her younger brother, John (Nathaniel Moreau). As a result, her schoolwork suffers and her personal life is nearly nonexistent.

Vannicola, who looks like a young Joan Jett, is exceptionally subtle, registering gradations of shame and despair on her face. Her Maggie is wonderfully ordinary, neither too precocious nor too much a victim, and therefore all the more believable.

The teleplay, by Dennis Foon and Judith and Garfield Reeves-Stevens, attempts to dramatize recent research about the children of alcoholics, the painful cycles of guilt, anger, and fear they endure as they try to keep their parents’ alcoholism a secret from the outside world.

The script is a well-intentioned effort, but too often Maggie and John spout psychobabble speeches that seem far too sophisticated for them.

Still, Maggie’s Secret gets a lot of the details right, which means that it depicts the life of a young person so hurt, confused, and unhappy that it seems rude to be watching her. The hour’s hastily arrived-at happy ending is insulting to the viewer — no problem this major is solved with a single heart- to-heart, daughter-parent chat. It’s also a merciful gesture, though, a respite from all the pain we’ve been watching. B+