That crazy monkey has carried off your girlfriend. You've got to climb ladders, ride elevators and not get hit by barrels, fireballs and mudpans while trying to reach the top of the screen and rescue your girlfriend.
This is a Donkey Kong clone with a few extras thrown in. If something moves, don't touch it. If it doesn't move, it's either a hammer (for bashing barrels) or a bonus item for picking up (umbrella, purse, etc.).