Ricky Gervais (who also co-wrote and co-directed) plays a man living on a parallel Earth where everyone is incapable of being other than honest. No lying means no acting, so all movies are documentaries and a movie star is someone who sits in a comfy chair and reads a fact-filled lecture into the camera. Gervais is employed as a screenwriter specializing in medieval history. His secretary (Tina Fey), as truthful as everyone else, often reminds him that he’s a failure and likely to be fired soon.
Gervais manages to secure a blind date with a woman he’s admired from afar (Jennifer Garner), but when he comes to pick her up she of course tells him straight out that she doesn’t find him attractive. At the restaurant their waiter points out that she’s out of his league. But when he takes her home she says that she had a nice time, much better than she’d expected. She then adds that she has had a lot to drink and will probably think differently in the morning.
Soon his secretary’s prediction comes true and Gervais is fired — his Black Plague film was not a box-office success — and then his landlord tells him to get out. He goes to his bank to withdraw his last remaining funds and in his distress he finds himself telling a lie, something that astonishes him. There’s not even a word for it in this world.
When he tries to describe the experience to a couple of friends they can’t even grasp the concept, and when he demonstrates by making obviously false assertions they still believe everything he says. As an experiment, he approaches a gorgeous woman on the street (Stephanie March, formerly the strikingly beautiful tall blond assistant district attorney on Law & Order: Special Victims Unit) and tells her they have to have sex right now or the world will end. Shocked, she exclaims, “Do we have time to get to a motel or do we need to do it right here?”
It turns out they have time, but Gervais discovers that he doesn’t want to go through with it. He’s the world’s first liar, but he’s still a decent person.
Then an unexpected disaster strikes. His beloved mother has a heart attack, and her doctor quite casually informs her that she’s unlikely to live through the night. She tells Gervais how terrified she is of dying, so to give her some comfort and hope, he lies and makes up an afterlife. The scene is thought-provoking, very moving, and memorable, in large part thanks to the convincing performance of the woman playing his mother, Fionnula Flanagan. Gervais isn't bad either. This is the best scene in the film.
Much of the rest (especially the first half-hour) is hilarious, but as that last bit indicates, the movie also uses its premise to make some serious points. On the other hand, I have to admit it at times gets repetitive, trite, and silly. I doubt everyone will like it, but I did.
Also, the trailer is worth seeing for the last line.