When Daniel Glass is misdiagnosed with a fatal disease he begins to notice how everyone around him treats him better, so he decides to keep pretending that he really is sick. This leads to more lies, and, eventually, crimes.

Sick Note is the story of Daniel Glass (Rupert Grint), a compulsive liar stuck in a failing relationship and a dead-end job where he's under the thumb of his irrepressible boss Kenny West (Don Johnson). And just when things couldn't get any worse, he's diagnosed with esophageal cancer. However, everyone starts to treat him better because of his diagnosis and he suddenly finds that life has new zest. But then he finds out he was misdiagnosed by the most incompetent oncologist on Earth, Dr. Ian Glennis (Nick Frost), Now he has a big decision to make: come clean and go back to his old rubbish life, or keep this new information a secret and pretend to be ill. He picks the latter, but the lie rapidly spirals out of control and both Daniel and Dr. must spend every waking minute trying to prevent the truth from getting out.