Prince Rico, the heir to a kingdom, and his bodyguard, Henry, enter the 9th floor of Hotel Zanzibar. Rico enters room 911, and after Henry enters room 912, Rico "orders" a prostitute. Alice, an old woman who suffers from memory problems, leaves her room and knocks on room 915, and Mr Green answers the door. Her son, Robert, comes out and brings her back to room 918.
Amber and her boyfriend Gus enter the 9th floor. Gus looks identical to Prince Rico. Gus goes back down to reception to replace a broken keycard, and the maid, Colette, helps Amber enter room 913. Rico changes rooms to room 914. Mr Green, planning suicide, opens his door and asks Colette for a bath plug. He had twin sons, both given up at birth, one of whom was sent abroad while the other stayed in England.
Gus comes back with a new keycard and discovers that it does not work. Fred, the bellboy, mistakes Gus for Rico, and sends him to room 911. Gus has ordered an apple tart with a diamond ring to be placed in it, and intends to propose to Amber with it. Alice leaves her room and knocks on Rico's room, and he thinks she is the prostitute. Amber comes out of her room, and, mistaking Rico for Gus, slaps him in disgust.
Henry comes out of his room to assassinate Rico. He hesitates for long enough for the prostitute, Tracey, to enter the scene. He tells her to pour a sedative into a glass of wine and make Rico drink it. Henry knocks on Gus's room, and brings Tracey, the "tart", into the room.
Colette and Vince, a hypnotist, enter the 9th floor. She convinces him to make Amber fall in love with the next person she meets, and they enter her room. Rico has "finished" with Alice, and she enters room 917. Tracey leaves Gus's room, with Gus horrified at his "experience". Fred comes, and insists that he pays for the "service". Tracey sets down the glass of wine, and demands a meal. Fred gives her the apple tart, replacing the plate with one of leftovers. They enter room 917.
Vince, having finished the hypnosis, picks up the glass of wine and enters room 916. Colette knocks on Rico's room, and he leads her in. Fred leads Alice back to her room. Robert knocks on Amber's room, and she falls in love with him. Colette and Rico leave his room, still mistaking Rico for Gus, and tries to convince him to get back his "girlfriend", Amber. Tracey leaves the room and demands payment from Rico. Fred and Colette try to sort the situation out, and enter Vince's room, while Rico enters Henry's room.
Gus comes out of his room, and Amber is angry with him for having sex with Alice. Attempting to defuse the situation, Gus presents the leftovers, while Fred and Colette carry a sleeping Vince out. Tracey attempts to slap Amber, and slaps Alice instead, bringing back her memory. Gus gives Amber a "true love's kiss", and breaks the spell. Rico comes out of room 914, and everyone is stunned by the similarity between Gus and Rico. Alice screams and Mr Green comes out in anger, and realises that Gus and Rico are his twin sons.
Henry suddenly holds a knife to Mr Green. Vince wakes up and recognises Henry. Earlier, Vince had hypnotised those who saw his show so that when they heard him say "Spaghetti Bolognese" they would sing and dance the hokey-cokey. Henry had attended Vince's show, so Vince uses this trick on him, and Henry drops the knife and starts singing and dancing. Rico and Fred grab him and lock him in his room till the police can be called. A toilet flushes, Tracey brings out the diamond ring, and Gus puts it on Amber's finger.
