It's almost midnight. Indiana Jones and Marion have been captured by Belloq and Toht's goons. However, just as they reach a cavern, a beam of light appears behind them, and out of it comes the legendary serial killer, Jason Voorhees, who slays his way through the goons before confronting Indiana Jones. They fight all over the cavern, eventually knocking the lid off of the Ark of the Covenant.
The spirits of the ark emerge from it, followed by the pillar of fire, and Jones advises Marion not to look no matter what as the ark unleashes it's power. When the chaos is over, however, Jones and Marion find that Jason wasn't affected by the ark at all, and Jason continues his assault, eventually killing Marion.
Jones strikes at Jason with his whip repeatedly, but this does nothing to stop the hockey-masked serial killer. Jason then pins Jones to the wall of the cavern, but before he can deliver the final blow, another light appears, and Jason is sucked into it, and Jones limps out of the cavern, exhausted from the day's events.