Setting: New Hampshire, early 1960's, on a river.The narrator absolutely adores a girl named Sheila Mant. After he finally works up the courage to ask her out on date to watch a band, she says yes. He decides to take her there on a boat, and brings a fishing pole to fish on the ride there.
Sheila tells the narrator she thinks fishing is stupid. The narrator forgot about the fishing pole he put on the boat. A fish bites the bait and the narrator tries to hide it from Sheila so she doesn't think he is stupid. But, it is the biggest fish he has ever caught, so he has mixed emotions about reeling it in or letting it go.
As the narrator deals with internal conflict between letting it go or keeping it, tensions rise. The fish starts swimming and it is so big, it pulls the boat. Sheila is starting to get suspicious.
When Sheila and the narrator reach their destination, the narrator decides to cut the line and let the fish go. He wants to impress Sheila so bad, so he gives up the biggest fish we would've ever caught.
When they arrive at the dance, Sheila ditches the narrator for another boy. The narrator gets very upset and decides to leave.
In the end, the narrator regrets his decision of cutting the line. He learns that you should not have to give up something that you love to impress anyone. There will be way more girls, but there won't be another bass that big.