At the beginning of Majora's Mask Link is riding Epona (his horse) through a forest. He is in search of a friend with whom he parted ways a few months earlier. All of a sudden, two fairies fly out in front of Epona, causing her to throw Link off her back. Link is knocked unconscious. A mysterious character wearing a strange mask walks up to him and starts looking through his possessions. He pulls out the Ocarina of Time and starts playing it. Link wakes up and sees the odd character, but he escapes on Epona before Link can catch him. He chases after the masked child and falls into a pit along the way. The pit is a portal to another dimension. When Link lands, he sees the strange character floating with the two fairies. Just before he escapes, he turns Link into a Deku Scrub, a plant-like creature that usually lives in a wooded area. Even worse, Link finds out that the world into which he's been transported will end in three days because for some reason, the moon is falling towards the earth. He has 72 hours to save the world.

Majora's Mask takes place a few months after Ocarina of Time. It is very similar in terms of gameplay. If you liked Ocarina of Time, chances are you'll like this game too. The major difference in this game, however, is that there is a time limit... sort of. The moon will fall to the earth in three days, but once you get the Ocarina of Time back you can travel back to the beginning of the first day whenever you want. The game automatically saves when you go back in time. The catch is that all limited items will be lost - things such as arrows, bombs, Rupees, bombchus, etc. (The number of items you have will go to zero, but you'll still have the ability to use the items once you've found them for the first time.) Temples will also reset, meaning you have to complete each temple within a 72 hour time limit. 72 hours game time, that is. An hour in the game is roughly a minute of real time. You can, however, slow down time so that an hour of game time is over two minutes. The game can also be saved at Owl Statues. If you use the Owl Statues to save, the game will save everything as is (meaning you keep all your items, and you don't go back to the beginning of the first day). These can be useful if you're in the middle of a temple and have to shut the game off, but there's a catch. If you save at an Owl Statue, shut the game off, start playing, and forget to save before shutting the game off again, not only will everything you've done be lost, but the next time you start the game you won't be at the Owl Statue, you'll start back at the beginning of Day 1 with no items and everything else back to normal. So if you've partway through a temple and you save at an Owl Statue, remember to save before turning off the N64 the next time you start your file.
One of the other major differences in this game is that it relies heavily on the collection of masks, some of which can turn you into different characters. Most masks in the game are just worn, but the Deku, Goron, and Zora masks will transform you into a member of their respective races, each giving you different abilities which are necessary to complete the game. For a better description of each mask character, visit the section called The Characters.
Returning are the classic weapon upgrades and Heart Container Pieces to find. The Gold Skulltulas return, but instead of running around the entire world trying to find them, they are located in special houses. There are also 24 masks to find. Not only that, but there are lots of new minigames, each either completely new or an upgraded version of its counterpart in Ocarina of Time. With only four temples, the main quest isn't as long, but if you want to find everything (without any help), you'll be playing for at least 50 hours. Like I said, if you liked Ocarina of Time you'll like this game, but I personally didn't enjoy it as much. Still, it's a great game that no Zelda should pass up.