James Bowen is a homeless man and former heroin addict, living on the streets of London and down to his last bits of change. After a life-threatening drug-related incident, his support worker Val gets him into a council flat and prescribes him methadone in an attempt to get him off the street. On his first night in his flat James discovers a cat rifling through his food. Assuming the cat had escaped from somewhere, James tries to return the cat to his real owners.
After letting him go, that same evening the cat returns to James's flat, this time with a purulent wound on his back leg. Worried, James consults his animal-loving but allergic neighbour, Betty. She informs James of a local charity vet where she volunteers, and names the cat Bob. Waiting on a queue at the vet, James misses a meeting with Val.
After the appointment, James has Bob neutered and sets him free. However, Bob keeps following James into town, eventually drawing more crowds of people, making James more wealthy, and he eventually decides to keep Bob. Bob becomes a tourist hotspot and James and Betty start to become romantically attached.
One night while returning home, James finds his old friend, Baz, unconscious on his flat estate, overdosed on heroin. Baz later dies in hospital, and James finds out that Betty cannot be around drug addicts, as her deceased brother had been one. On New Year's Eve, James makes an impromptu visit to his biological father, Jack, his stepmother, Hilary, and his lost sisters, Pris and Faith. After Bob destroys their living room, Hilary sends James and Bob out.
One day, while busking, James gets into an argument with a thug causing the crowd to get in a brawl with the man and James getting arrested for it. Although found innocent, he is prohibited from busking for six months. At the pharmacy where he is waiting to receive his methadone, Betty notices James; they argue and go their separate ways. Later, James visits the offices of The Big Issue to make some more money for him and Bob. He regains his popularity with tourists by selling The Big Issue.
After being accused of illegally selling magazines on another vendor's patch, James and Bob are banned for a whole month. After going back in business James gets into an argument with a rude woman trying to buy Bob off him, losing Bob in the scuffle. Bob does not return for a few days, leaving James devastated. After Bob returns, James feels he is ready to come off the methadone.
After a week of gruelling withdrawal symptoms, James awakes clean and healthy. He goes to visit Betty, who is in the middle of moving and living a life meant for her to live. James and Betty end on a good note. A journalist, Mary, requests to write a book about James and Bob after his Internet and media popularity, and James agrees.
James then fixes up his relationship with his father Jack, and his life turns around for the better. Later, at a book signing, James is celebrated by Val, his father, and a visiting Betty. James and Betty remain supportive friends as James and Bob continue on their journey together.
Luke Treadaway as James Bowen
The real James Bowen makes a cameo appearance, asking an autograph from his character
Bob as himself
Stand-ins for Bob: Oscar, Booker, Jafffa, Leo, Ricki and Trayce
Ruta Gedmintas as Elizabeth "Betty" Robinson, James's animal-loving neighbour and love interest
Joanne Froggatt as Val, James's drug support worker
Anthony Head as Jack Bowen, James's remarried father
Beth Goddard as Hilary Bowen, Jack's wife and James's stepmother
Caroline Goodall as Mary, an American journalist who persuades him to write a book about Bob
Darren Evans as Baz, James's old friend who did not recover from heroin addiction
Ruth Sheen as Elsie, a kind middle-aged woman, who gives presents to Bob
Nina Wadia as Bus Conductress
British biographical drama
based on the book of the same name and The World According to Bob by James Bowen.
A Christmas-themed sequel, A Gift from Bob, was released to UK theatres in November 2020. The film was released posthumously, as Bob the cat died in June 2020.