In his laboratory on Cannery Row, along northern California's Pacific coast, Doc, a marine biologist, views the world much as he views the specimens in his lab, believing that it takes All Kinds of People. He explains this to his two friends, Mac and his sidekick, Hazel (a man, but so named because his mother ran out of boys' names) and demonstrates his point with The Tide Pool. His discourse is interrupted by the arrival of Suzy, a vagrant who cut her hand while breaking a store window in order to steal some food. As Doc bandages her up, he learns that Suzy is homeless (Everybody's Got A Home But Me) and she gratefully accepts an invitation to move in with Fauna, the warm-hearted proprietress at the town's only hotspot, the Bear Flag Cafe.

A few weeks later, down at the Flophouse where Mac, Hazel and the rest of their buddies hang out, a discussion of their easygoing, unemployed lifestyle is underway (On A Lopsided Bus) when Mac tells them of a dilemma facing Doc: to advance his research he must get a hold of a special microscope, and Doc doesn't have the $300 to buy it. Mac hatches a plan: he will devise a phony raffle to sell off the Flophouse and use the money for Doc. The gang returns to its philosophical reverie and when Fauna drops in for a visit, the discussion turns into a spirited war of words on the battle of the sexes - The Bum's Opera.

Back at the lab, Suzy has become a steady visitor. She brings Doc a cake, clearly homebaked despite her denials and, when he gently teases her about her affections for him, she becomes defensive and hits Doc where it hurts - right in his career. Alone, Doc reflects on where his life has taken him (The Man I Used To Be) and decides that he wants Suzy in his life. Fauna, who wants to see these two young people together, helps Doc in his pursuit. She is delighted when her plan works out (Sweet Thursday) and then shifts her attention from Doc to Suzy, giving the girl a much-needed pep talk (Suzy Is a Good Thing) before the big date.

The whole town turns out to spy on Doc the night he picks Suzy up for dinner but finally they are alone together and realize that they might be falling in love - All At Once You Love Her.

The Bear Flag Cafe is more than a friendly dining spot; it is, as Fauna and the girls decide, The Happiest House On The Block. As the town prepares for Mac's big raffle (The Party That We're Gonna Have Tomorrow Night), Fauna - in her ongoing campaign to hook up Doc and Suzy - arranges an elaborate pageant to be presented at the Cafe during the festivities, with Suzy dressed up as Snow White and singing a number, Will You Marry Me?, aimed at Doc. The plan backfires when, in the middle of the pageant, Suzy's nerve fails her; humiliated, she runs away, taking refuge in, of all things, an empty boiler pipe down on the beach.

There is trouble afoot and Hazel, for one, is determined to figure it out - Thinkin'. Meanwhile, back at the Cafe, Fauna consoles Doc (All At Once You Love Her - Reprise) while his friends back him up with moral support - How Long? With renewed confidence, Doc visits Suzy in her boiler pipe home. Pride gets the best of both of them and, rather than fight or make up, they pretend to be relieved that it can't work and assure each other that they have learned from their mistakes - The Next Time It Happens. Doc leaves, not seeing that Suzy's tears speak louder than her words. Hazel climbs into the pipe now and confronts Suzy - he can tell that Doc is unhappy, so what would it take to bring them together? Suzy insists that Doc doesn't need her, and that she would only go to him if he was in trouble, if he broke an arm or a leg, for instance. That is all Hazel needs to hear. Thanking Suzy, he makes a quick retreat.

Overnight, a mysterious intruder has broken Doc's arm with a baseball bat! Hazel isn't saying a word but, sure enough, Suzy is now over at Doc's lab, taking care of him and nursing his wound. Their romantic reconciliation is interrupted by the whole town again, this time triumphantly presenting Doc with the gift purchased from the raffle winnings. True, it's a telescope and not a microscope, but it's the thought that counts - Finale: Sweet Thursday (Reprise).