 A paramedic is let into a house to the sounds of panic . Earlier , the fastidious Angela prepares to host a party for the 79th birthday of her mother , Maggie . Angela 's daughter , Katie , heads to her room to complete her homework . When Angela moves a cake , she reveals the head of Jim , her husband . Jim plans to play a trick on Pat — a practical joker and the husband of Angela 's sister , Carol ( a recovering alcoholic ) — by hiding under the cake . Maggie , Carol and Pat — the latter wearing a wolf mask — arrive at the house . As the three settle , Pat plugs in his mobile to charge — something Jim had asked Angela to prevent — and secretly places ice in a bucket . Carol privately drinks from a sunscreen bottle while ostensibly unblocking the toilet after her mother could not flush it . Angela is proud that the party food is from Marks 's , but Carol mocks Angela 's middle class affectations . Maggie wants a photograph with the food on the table , and Carol lights the cake 's candles , which burn towards to the flammable fake cake — under which Jim is still hiding . Katie greets her nana and aunt , with Maggie insisting that she tell the joke from Pat 's card . Panicking , Angela blows out the candles . The room clears , and Jim is left frustrated . 
