Happy family with two children, a beautiful wife - what more could wish a respectable family man? Evan Webber constantly immersed in the work, and so it was on that fateful day. The whole family left for a vacation on the beach, and he was to disassemble the backlog of cases. There were no signs of heavy rain, but nevertheless the weather sharply deteriorated ... the door insistently and loudly knocked. It turned out to be two young, very attractive person, one blonde, the other - a brunette. Girls were soaked and shivering. The protagonist of the film "Knock Knock", Being a gentleman, kind and understanding person could not leave the guests for the threshold. However, no man did not foresee the consequences. For his part, it was only a sign of decency and good manners. By offering the ladies shelter, Evan makes the most dangerous in the life of an error. Soon, his peaceful existence is destroyed, and then comes chaos. What did these girls?