Knight and Day has two principal characters: Roy Miller, (Tom, the Man, Cruise) and June Havens (Cameron, the thirty-seven-year-old, Diaz).
Cruise is an American spy gone rouge. He has supernatural powers. Diaz is a blond mechanic.
Cruise and Diaz bump into each other at the Wichita Mid-Continent Airport. They flirt – instant chemistry. And it just so happens: They’re on the same flight to Boston.
Up in the air, they make small talk. Cruise falls for Diaz.
Diaz goes to the bathroom. While she is powdering up, Cruise rashly decides to murder everyone on the plane (including the pilots) so he can kidnap Diaz.
Cruise has a drink (gin). Then crash lands the plane in a field. He roofies Diaz. Just before she loses consciousness, Cruise explains whatever anyone (viz. the U.S Government) says about him is a lie:
They will tell you a story about me. How I am mentally unstable. Paranoid. Uh, violent, and dangerous. It will all sound very convincing. Don’t believe them.
Things then get complicated. We learn Cruise possesses a one-of-a-kind C-size solar battery. He was flying to Boston to catch a connecting flight to the Maldives where he owns a private island and was planning on living out the rest of his life, using the battery as his main energy source. He now needs to get his hostage and himself there. The problem is intensified by the fact a lot of other people want this battery:
- The President of the United States (played by a black African American woman) wants it to power Wi-Fi hot spots in rural areas.
- European terrorists want it to help them build a bomb to blow up Heathrow International Airport.
- The engineer of the battery, Simon Feck, wants it back so he can build a high-speed train from Spain to Russia. He plans to call the train service “Knight and Day: Spain to Russia.” Hence the title of the film.
All these parties then go after Cruise. (And now the guilty-by-association Diaz). This leads to a lot of explosions, gun fights, car chases, and so on as documented in the trailer:
Eventually, Cruise gets Diaz to his island. But they have a fight. Diaz is sick of being kidnapped, drugged, and fondled:
Cameron: How long have I been out?
Cruise: 18 hours.
— Where am I?
— My place…
— You drugged me again, Tom. You can’t do that.
— You weren’t coping well…
— What am I wearing?
— A bikini. We’re in the tropics.
— How did I get in the bikini?
— Cameron, I’ve been trained to dismantle a bomb in the pitch black with nothing but a safety pin. I think I can get you in and out of clothes without… Looking. That’s not saying what I did though.
Diaz tries to punch Cruise. Then runs away. She is upset. She takes an incoming call. The U.S government traces it, and then attacks Cruise’s private island. Cruise and Diaz jump in the ocean and swim to Austria. Something happens in Austria. Then something happens again. Diaz is drugged again. A bomb goes off. A Muse song plays in the background. Something happens with a motorcycle. Then, somehow, the European terrorists acquire the battery and fly off with it.
Turns out the battery is actually a bomb, though. So the terrorists get blown up by the battery-bomb. The engineer, Simon, makes a new battery. This battery actually works. The U.S Government installs Wi-Fi in rural areas and Tom Cruise and Cameron Diaz move to a private island in the Maldives where they live off the land, and the battery. We never find out if the train system from Spain to Russia was developed.