In the deep jungles of darkest Peru, a British geographer named Montgomery Clyde happens upon a previously unknown species of bear. He is about to shoot it to take back a specimen to England when another bear playfully takes his gun away. He learns that this family of bears is intelligent and can learn English, and that they have a deep appetite for marmalade. He names them Lucy and Pastuzo. As he departs, he throws his hat to Pastuzo and tells the bears that they are always welcome should they wish to go to London.Years later, the two bears are living in harmony with their nephew when an earthquake strikes their home, forcing them to seek shelter underground. Distracted and upset at the loss of his home, Pastuzo is unable to reach the shelter in time. He disappears, with his hat being found the next day by his nephew. Aunt Lucy encourages her nephew to go and find solace in London, and stows him away on a cargo ship, after which she says she will move into the Home for Retired Bears.The young bear reaches London, but he fails to find a home. He is taken in briefly by the Brown family, who name him after Paddington Station, where they found him. Henry Brown, a devoted risk analyst, is adamant that Paddington (Ben Whishaw) stay only one night while they find a place for him to live permanently. Paddington causes a series of accidents across the house, further isolating himself from the Browns.Paddington thinks he can find a home with the explorer who found his aunt and uncle but does not know the explorer's name. Mary Brown (Sally Hawkins) takes Paddington to an antique shop owner who discovers that the hat bears the stamp of the Geographers Guild, but the Guild says that it never sent a member to explore darkest Peru. With the help of Mr. Brown (Hugh Bonneville), Paddington infiltrates the Geographers Guild archives and discovers an expedition to Peru was undertaken by Montgomery Clyde. He uses the city's phone books to track the addresses of all the "M Clyde's" in London.Meanwhile, a sadistic museum taxidermist named Millicent Clyde (Nicole Kidman) captures, kills, and stuffs exotic animals to house in the Natural History Museum. When she becomes aware of Paddington, she immediately sets out to hunt him down. The Brown family departs for the day, leaving Paddington home alone. Scheming with the Browns' nosy neighbor Mr. Curry, Millicent sneaks in and attempts to capture Paddington; he inadvertently repels her, but burns the kitchen in the process. Oblivious to Paddington's statement of Millicent's capture attempt, the Browns state that he must move into a new house as soon as possible.Feeling unwanted at the Browns, Paddington leaves and attempts to track Montgomery Clyde himself. He finally locates the house, only to discover that Clyde died many years ago, and that Millicent is actually his daughter - who resents her father for losing his job and membership with the museum; out of a change of heart, he refused to bring a valuable Peruvian bear specimen home, even though it would have made him the wealthiest man in the world.Millicent is determined to succeed where her father failed and become rich and famous herself. She tranquilizes Paddington and prepares to stuff him, but when Mr. Curry discovers her true intentions, he informs the Brown family, and they rush to save Paddington. They rescue him, and Paddington subdues Millicent by throwing a marmalade sandwich at her, which attracts a huge flock of pigeons, distracting her as family relative Mrs. Bird (Julie Walters) opens a roof hatch and inadvertently pushes her off of the roof, trapping her on a flagpole.In the aftermath, the Browns adopt Paddington into their family and Millicent is sentenced to community service at a petting zoo. Paddington writes to Aunt Lucy saying he is happy and has finally found a home.