The House in Nightmare Park

Struggling actor Foster Twelvetrees is invited to the Henderson family’s country home to perform a dramatic reading for the family. The invitation seems courteous, but the family’s eyes reveal a deeper interest in him as a possible instrument in their scheming over Victor and the estate. He arrives to begin the night's events with a mix of nerves and expectation.

Earlier in the day, Stewart secretly slices a poster of Twelvetrees, signaling a darker, possessive attitude beneath his friendliness. The gesture is small but charged, hinting at a power struggle within the family. Twelvetrees remains largely unaware as the social flirtation continues around him.

Jessica and Patel rummage through Twelvetrees' luggage, trying to uncover something secret or valuable. The covert search contrasts with Foster’s bumbling charm and sets up a sense that something crucial is being hidden. The discovery (or lack thereof) foreshadows hidden motives tied to inheritance.

Stewart scolds Twelvetrees for nearly entering a restricted room, explaining that Victor—the ill brother—is kept inside. The room’s secrecy hints at a larger family conspiracy and the fragility of the will around the estate. The tension escalates as the hidden truth presses closer.

That night, Reggie and his daughter Verity arrive demanding their usual allowance, while Stewart is seen slipping away to check on his mother. Her presence adds a chilling, secretive edge to the household’s dynamics. The stage is set for the events to come.

The next day, after an introduction to the snake house underground, Twelvetrees secretly climbs to see Stewart’s mother behind a locked door. She tries to kill him with a knife, but Patel saves him and explains her secret existence. Despite the shock, Stewart convinces Foster to stay and perform that evening.

Ernest and his wife Aggie arrive alongside Reggie to demand his regular allowance, noting Victor’s cheques have bounced. They suspect Stewart is manipulating Victor’s will and decide to stay to watch for any sign of changes. Their greed intensifies the tension within the house.

Verity urges Foster to check on Victor and they discover the bed is a dummy. Stewart drops the bomb: Victor is dead and Foster is his secret son, heir to the estate, with a possible clue to diamonds hidden on the property. Suspicion and ambition converge as the true stakes emerge.

Ernest and Aggie, convinced they’ve found a clue in a misquoted motto, plot to poison Twelvetrees. Stewart foils the plan and shows they know enough to threaten the diamond secret. The family’s greed spirals toward more violence.

During a Henderson family performance, Ernest is stabbed in the back and dies, shocking everyone. Foster flees in panic and is pursued by Verity, who aims to pin him to the escalating turmoil. The murder tightens the net around all the survivors.

Verity guides Foster back to confront Jessica and the suspicious motto; she helps him realize the clue lies in his own name. Foster learns his real name is Nigel Anthony Julian Amadeus Henderson, confirming the clue is tied to his identity. Verity hints that his initials form NAJA, a snake genus, linking to the diamonds.

Foster attempts to enlist help from the police but loses his way in the forest. He finds Patel, who volunteers to go in his place in the search for the diamonds. Patel, having borrowed some of Foster’s clothes, is mistaken for Twelvetrees by the Henderson mother and killed as he walks through the woods.

Back at the house, Foster reunites with Verity and faces Jessica, who holds the motto. Aggie lies dead near the snakehouse as the truth about the nickname and the birth certificate surfaces. Foster retrieves the so-called clue, but the map has already burned away, leaving the diamonds as an elusive prize.

Stewart, Verity, and the Henderson mother are taken away in a police cart, ending the immediate danger. A final shot lingers on Foster beginning to dig in the estate’s grounds, suggesting the diamonds are still out there and the hunt continues beyond the film’s end.