Richard Gadd plays Donny, a failing London comedian who gets entangled with a relentless stalker named Martha.
In 2015 in London, while working at a pub, struggling comedian Donny Dunn gives a free cup of tea to a distraught customer. The customer, Martha Scott, becomes a regular, claiming she is a wealthy lawyer and entertaining Donny with stories. She becomes increasingly flirtatious, calling him “Baby Reindeer” among other nicknames. She begins emailing him hundreds of times a day, making him uncomfortable. He reluctantly takes her for coffee but is disturbed when Martha has a public outburst.
He follows her home, discovering she lives in a cluttered apartment on a council estate, and flees after she notices him. Martha views this as a development in their relationship. She shows up uninvited to Donny’s performance at a local comedy competition, and her interruptions help him secure a position in the semi-finals. She confesses her love to Donny, has another outburst when he tries to let her down politely, and sends him a friend request on Facebook. Donny discovers that she is a convicted stalker. He nevertheless accepts her friend request.