Set is annoyed at the Super Mutant presence in Necropolis and tries to recruit the Vault Dweller to take care of the problem. He is not mentioned in the Vault Dweller's memoirs, but the Vault Dweller did kill the super mutants, which led to the slaughter of everyone in Necropolis, including Set himself.
The game takes place in the year 2161 on the West Coast of what used to be the United States of America, particularly in California. It begins in Vault 13, the protagonist's home. Vault 13's water chip, a computer chip responsible for the water recycling and pumping machinery, has broken. Armed with a PIPBoy 2000 and meager equipment, the protagonist is sent out into the remains of California to find another water chip.