The House of Clocks

An elderly couple, Victor (Paolo Paoloni) and Sarah (Bettine Milne), live in a rambling country house filled with clocks of all shapes and sizes. The couple's taciturn grounds man Peter (Al Cliver) is happy enough looking after the slavering pack of dogs the couple own. But the maid Maria (Carla Cassola) is becoming more and more suspicious of her sinister employers that they are hiding something. Sure enough, she discovers the dead bodies of a money-grabbing nephew (Paolo Bernardi) and his wife (Francesco De Rose) lying preserved in open coffins in the wine cellar. Maria is gorily killed by the elderly Sarah in the greenhouse the next morning while announcing her plans to quit.Meanwhile, three hoodlums, Diana (Karina Huff), Tony (Keith Van Hoven) and Paul (Peter Hintz) are driving through the area and decide to rob the old couple's house after receiving a tip-off from a grocery store owner in a nearby town about the wealth it supposedly contains and the decrepitude of the owners. That evening, Diana cunningly talks her way into the household by pretending that her car has broken down nearby and asks to use the phone. Soon, the phone lines are cut by her male accomplices and they force entry through an open window. Their plans to rob the old couple go badly wrong when Peter intervenes with his shotgun. A bloodbath ensues with Sarah accidentally getting shot, Peter getting killed by Paul, and Victor attacks Tony, forcing Diana to shoot him dead. The young trio are horrified by this turn of events, but decide to bundle the bodies away in a cupboard.At first the dazed criminals fail to notice what effect the mayhem has had on all the clocks in the house. Each clock stops at 8:00 PM, the exact time the couple were killed. When they do notice, they try to leave, but are trapped indoors by the Dobermans let loose to prowl the grounds. Stranger still, the clocks begin to move in reverse, first slowly, then faster. The three decide to relax in the house overnight, and they head off upstairs to smoke some joints. Diana and Tony get a little too drawn into it and start to make out with each other, and soon begin to have sex.Paul, who is left out of the lovemaking, wonders dejectedly downstairs. He discovers the bloodstains on the dining room floor where the killings took place have disappeared, and then he sees the bodies lying back where they'd fallen. Before he can alert the others, Paul is shot by an unseen figure stalking the house. Hearing the gunshot, Diana and Tony quickly dress and rush downstairs and see the old couple reanimate and advance towards them. In the kitchen, Diana is trapped by the old woman who grabs a knife and stabs her through the hand, pinning her to the kitchen table. The old Sarah then retrieves a ring that Diana had stolen from her ring finger. Making a narrow escape, Diana and Tony find a severely wounded Paul in the cellar. Illogical time distortions continue as Diana's hand heals up while Paul's injuries remain. Diana and Tony escape from the cellar through a high window and emerge into the grounds. Paul is too injured to hoist himself up to the window and is axed to death by the vengefully reanimated Peter. As the couple run across the grounds, now in daylight with the clocks in full reverse, Tony is pulled into a shallow grave by the corpse of Maria, the maid. She kills him with a wooden stick though his stomach before heading off to confront the old couple. In the wine cellar, Maria confronts the elderly couple with murdering their nephew and his wife to remove them as their rightful heirs to the estate. Then, the niece and nephew finally revive and the old couple are killed again by their previous victims. Diana staggers away from the house.Suddenly, Diana, Tony, and Paul awaken in their car outside the country house. Apparently all that that happened to them was just a dream brought on with special intensity by the marijuana they've been smoking. Inside the house, the fully alive nephew and niece enjoy being alive again and are having their morning breakfast, with Maria the maid attending to them. The dead bodies of Victor and Sarah are in the wine cellar having been substituted for them.Driving away from the house, Diana, Tony, and Paul remark on the astonishing similarities of their dreams of being at the house and time moving backwards. Suddenly, a dead cat they picked up on the road earlier suddenly revives and attacks them, forcing Tony, who's driving, to crash their car off a cliff and killing them all... again?! Inexplicably, the car's clock and all the wristwatches on the bloodied and dead Diana, Tony, and Paul stop, and begin to roll backwards...Quote from Honoré de Balzac: "If time turned back, our sins would also have to start anew."

Question: What drug induced them to have this dream?
Answer: Marijuana.