Handlung

Walter Mitty (Ben Stiller) is a negative assets manager (negatives of photographs) at Life magazine who frequently daydreams of fantastic adventures and has a crush on his coworker Cheryl (Kristen Wiig). In his daydreams Walter lives by his ethos of ABC which stands for Adventurous, Brave and Creative. He saves dogs from exploding building and imagines how that would make Cheryl come running to him.

Walter attempts to contact Cheryl via EHarmony but EHarmony customer service agent Todd Mahar explains that Walter's account is not fully filled out. Walter's "been there" and "done that" sections are blank. Walter lives a very boring life and hence has nothing to say in those sections.

The magazine has just been acquired & the new management is looking to downsize unproductive workers. Walter also has the habit of "zoning out" while having his adventure day dreams and this looks odd in front of Ted who is the MD of the transition team.

Walter works with legendary photojournalist Sean O'Connell, although they have never met in person. Sean O'Connell (Sean Penn), who works closely with Mitty concerning his submissions, has sent him a package containing his latest negatives and a wallet as a gift in appreciation of Walter's excellent work. Furthermore, that package contains a special photograph, negative #25, that he says in writing captures the "Quintessence" of Life and that it should be used for the cover of the magazine's final print issue as it converts to online status.

Unfortunately, that specific negative is missing from the package. Ted Hendricks (Adam Scott), the obnoxious manager of the magazine's transition, has also heard Sean's recommendation. When he asks about #25, Walter stalls and lies, worried about being fired. Ted Hendricks is also handling the downsizing. Walter then asks Cheryl for help, and she suggests that Walter use the other negatives as clues to Sean's location. He and Hernando (Adrian Martinez), his understudy, are stumped by a negative depicting a curve, until they notice another containing the name of a ship registered in Greenland. Walter reluctantly takes a plane there.

Arriving in Greenland, Walter goes to a bar asking about Sean. The bartender explains that he is already gone on a ship, and to find him, Walter would need to go on the postal helicopter, and the pilot is drunkenly singing a karaoke version of "Don't You Want Me" in the bar. Walter declines to fly with a drunken pilot but imagines Cheryl singing to him "Space Oddity", gains a new confidence. Mitty recognizes the pilot's thumb from one of the negatives, and after hesitating, joins the pilot on a trip to bring supplies to the ship.

Nearing the ship, Walter learns the helicopter cannot land onto the ship. Walter misunderstood the pilot thinking he had to jump onto the ship where there was a boat nearing to catch him but then dived instead into ice-cold, shark-infested waters, losing the ship's supplies and preventing radio communication when he finally comes aboard.

In doing so, he realizes this whole adventure is actually happening as opposed to his daydreams. Once on board, Walter learns that Sean is no longer on the ship although the sailors remember Sean, even offering Walter some cake he left behind. To his surprise, it is Walter's mother's clementine cake, her specialty. Walter discovers more clues in the wrapping newspaper. His journey continues to Iceland, where Sean has gone to photograph the volcano Eyjafjallajokull. Walter bikes, skateboards, and runs through the Icelandic countryside to find Sean. The eruption prevents Walter from finding Sean and he is forced to break off the search after receiving a text message calling him back to New York immediately.

For his failure, his first professional loss in his long career with the magazine, Walter is fired and is even more disheartened to find that Cheryl, who was let go earlier, seems to have reconciled with her estranged husband. He tries to visit Cheryl, but spots her ex-husband and leaves before talking to her. Walter returns home, thoroughly discouraged, and throws away the wallet when he visits his mother (Shirley MacLaine).

To his surprise, Walter recognizes the curve of the piano in his mother's house while looking at the last negative. When asked, she tells Walter that she met Sean and baked him the clementine cake. She had told Walter earlier, but he was daydreaming.

He then finds a new clue to continue to hunt for Sean. Mitty eventually tracks down O'Connell in the Afghan Himalayas, trying to photograph a rare snow leopard, and asks about the missing negative. Sean explains that the message about taking a closer look was literal: the negative was in the wallet. He decides not to tell Walter what the picture actually depicts. Walter joins him in a soccer game with some locals. He then flies to Los Angeles but is arrested by airport security for arriving from Afghanistan and calls the only person he knows in Los Angeles; Todd Maher (Patton Oswalt), a representative at EHarmony who has kept in contact through his adventures. The two chat and Todd expresses admiration for how adventurous Walter appears.

Walter returns home and helps his mother sell her piano, he mentions he does not have a wallet anymore. His mother says she always keeps his Knick Knacks and she produces the wallet he had thrown out. Without looking at the picture, an emboldened Mitty delivers it to Life magazine, tells management that it was the photograph Sean O'Connell wanted for the final issue, and berates Hendricks for disrespecting the staff that made the magazine so honored.

Walter reunites with Cheryl, and thanks her for inspiring him on his journey when they receive their severance packages and learns that Cheryl's ex-husband was only at her house in order to repair the refrigerator. Walking along the street, they see the final print issue on sale at a newsstand, and on its cover, they see the photograph from #25 for the first time: it shows Walter sitting outside of the Life building, examining a contact sheet; the magazine is dedicated to Life's staff, and Sean's note actually referred to "quintessence of Life". Walter and Cheryl continue their walk holding hands.