After the end of the world several people washed ashore, but a year later only Celes and Cid remain. Cid cared for Celes but succumbed to an illness. Celes catches a fish for Cid at the beach, and depending on the quality of the fish Cid consumes he will either live or die. If Cid dies, Celes attempts suicide by throwing herself off the cliffs to the north, but she hits the water and not the rocks.
After finding Locke's bandanna used to heal a seagull who lands on the beach when she washes ashore, Celes's hope is restored. She finds a note from Cid and a raft, which she uses to leave the island to search for her friends. If Cid lives, he shows Celes the raft himself, and begs her to search for other survivors.
Fast moving, healthy fish help improve Cid's condition, whereas the slow moving rotten/foul-tasting fish deteriorate his health. When the player is trying to save Cid the game keeps track of a counter for Cid's health, which starts at 120 and decreases by 1 every passing second, unless the player is in the menu screen or in a battle.
Feeding Cid fish lowers or raises the counter depending on the type of fish:
|Medium||A rotten fish||A foul-tasting fish||-4|
|Medium||Just a Fish||An ordinary fish||+16|
|Fast||A yummy fish||A delicious fish||+32|
If the player feeds him multiple fish at a time, the effects of all of the fish count. The type(s) of fish in the water is reset every time the player talks to Cid.
If the player doesn't save Cid, there's no way the player can make the fish reset because they need to talk to Cid to do that. So the player will not be able to collect all four fish under the Rare Items within the Items menu.
What Cid says spoken to depends on his "health" counter. If the player enters the cabin when the counter is below 30, Cid is dead when spoken to, but if the counter is over 30 when the player enters, but drops below 30 while they're in the room, Cid won't die until they leave and come back in. If the player feeds Cid fish which increases the counter to 256 or more, Cid will be saved.