For its first half, “Seeking a Friend for the End of the World” is as lost and out of sorts as its title.

But “Seeking” is a movie you have to give time to work. It was written and directed by the woman who wrote “Nick & Norah’s Infinite Playlist,” so you owe it that much.

Steve Carell stars as Dodge, an insurance salesman. And that adds to the confusion.

Do we laugh when, on hearing the news that a last-ditch space mission to stop the asteroid “Matilda” from crashing into Earth has failed, his wife leaps out of the car and runs away? Yeah, it’s a little funny.

The “End of the World” party Dodge attends is amusing and very depressing.

Everyone around him is giving in to impulses, acting irrationally. But all Dodge can do is be sad, wonder about the “love of his life” who got away (not his wife) and slap up fliers with his phone number on them.

“You’re going to die alone,” a friend complains.

“He’s going to die with everybody else,” is her husband’s comeback.

And then Dodge meets his neighbor. Penny (Keira Knightley) is many years his junior, a Brit whose flightiness and optimism have caused her to A) kick her boyfriend out and B) miss the last flight to the UK to see her family.

Penny resolves to help Dodge make one last contact with the one who got away. And Dodge promises to get her onto a plane home before The End.

Writer-director Lorene Scafaria aims for the sweet spot in this morbid setup.

We meet one of Penny’s exes, a Marine (Derek Luke). He’s surrounded himself with men from his unit and collected all the Smart Cars he can, for transportation after the asteroid ends Life on Earth.

The sunniest scene may be in a T.G.I.Fridays style-restaurant, where the staff, led by the charmingly goofy T.J. Miller of “She’s Out of My League,” goes on serving customers, getting drunk and throwing a rather giddy orgy.

By the third act, the tragedy and romance of it all start to pay off. Issues and feelings come out into the open. “Seeking a Friend” finally finds its footing, and seems to take its own message to heart:

“Better late than never.”