This is the very beginning of the game. On a train you arrive at a reactor with the rebel group AVALANCHE. You fight your way until you catch up to the others. You get into the reactor and you find out the names of your comrades, Biggs, Jessie, Wedge, and Barrett. You have to go inside the rector, and go to the core and set a bomb. After setting the bomb you fight a boss. After defeating the boss you escape the reactor and decide wether or not to save Jessie on the way out. After that, you walk into the town near the reactor and talk to a flower girl named Aeris. You then attempt to escape but you are confronted by many Shin-Ra soldiers. The only way out it so jump on a moving train that your comrades are in. After taht you go to the AVALANCHE hideout and meet tifa and Marlene.