When a struggling artist makes a Faustian type deal to sell his soul to the devil in return for a $10,000 painting competition prize the devil in the form of Mr Horn turns up at his and his wife Helen's home for a holiday. However the devil is not interested in his soul, he is more interested in the chaos he causes among humans in a world without sin as they come to realise that like mosquitoes the devil also has a place and a reason for being in the world.