Spoilers.
Tom Cruise and Jake Johnson are soldiers who find the Mummy's tomb. A hot blonde scientist shows up to retrieve the tomb, but their plane gets caught by a swarm of birds. Cruise saves the blonde and miraculously survives the crash.
As it turns out, the tomb holds an egyptian princess who swore revenge against her father after being denied the throne. She made a pact with the god of death, Set, to get supernatural powers in exchange for finding a vessel for Set, but got foiled and mummified. Now she has chosen Cruise to be the vessel.
Cruise is cursed and can't die. He meets the blonde's boss, Dr. Jekyll, who runs a secret organization that captures, studies and destroys monsters. The Mummy manages to escape and begins playing mind games with Tom. As it turns out, she needs to retrieve her mystical dagger in order to complete the ritual and turn Cruise into Set. Cruise and the blonde fall in love as they search for the dagger. Johnson dies.
Cruise and the Mummy are both recaptured by Jekyll after Cruise gets the dagger. Jekyll plans to kill them both. Cruise steals a serum that Jekyll needs to take, causing Mr. Hyde to emerge and kick his ass. The Mummy escapes again and chases Cruise and the blonde to an underground temple, where the blonde dies. Cruise fights the Mummy but gets his ass kicked. With no other option he stabs himself with the mystic dagger and becomes the vessel for Set.
Cruise kills the Mummy by draining her lifeforce and revives the blonde, but tells her they can't be together because he's now the god of death, but he will return once he finds a cure for his condition. The blonde later tells Jekyll that Cruise may now have the power of a monster, but he still has the heart of a man and will find a way to fight the darkness within and "others like him". Jekyll remains determined to catch him.
Movie ends with Cruise reviving Johnson. They reaffirm their bromance and ride off into the sunset ready to fight monsters.
