At a club in Manhattan, Elisha J. Whitney is waiting impatiently for his assistant to arrive with all his travel materials for Whitney to sail to England the next morning. Billy Crocker finally shows up — half an hour late — but he’s forgotten Whitney’s passport, which he promises to deliver first thing in the morning. Conspiratorially, as two Sailors dine in the background with Betty and Estelle, Whitney orders Billy to go to Wall Street in the morning and sell all the firm’s shares of Amalgamated Prestoleum. Billy is shocked, but Whitney assures him he’s had a hot tip that shares of Amalgamated are going downhill fast. Just as Billy is checking his messages with Casey, the host, Reno Sweeney enters the club looking for Billy — in the hubbub of his errand running for Whitney, Billy completely forgot about his date with Reno. Despite his faux pas, she invites him to sail to London with her in the morning (I Get A Kick Out Of You). Billy confesses to Reno that he’s fallen in love with a fantastic girl, and he needs to stay in New York to win her over. Reno is furious — she thought she was the one Billy wanted to marry. She storms off as the Sailors confess to Betty and Estelle that they’re leaving in the morning (There’s No Cure Like Travel).
One the deck of the S.S. American, the Captain, Purser and Deck Stewardess are dealing with a crisis: Charlie Chaplin has cancelled his berth and chosen to sail with the Mauretania instead. They frantically scour the guest list for another celebrity as the Reporters and Photographers complain. The Minister and converts Luke and John arrive on the ship, closely followed by Reno and her Angels. The Reporters and Photographers are excited by the arrival of debutante Hope Harcourt, English gentleman Lord Evelyn Oakleigh and Hope’s mother, Mrs. Harcourt, who announces that Hope and Evelyn are to be married on the ship. As they board the ship, they encounter Whitney and Billy, who is shocked to learn of Hope’s engagement. Whitney leads the party off to celebrate, reminding Billy to go to Wall Street and sell the Amalgamated shares. Before he can exit, two FBI Agents stop him, asking if he’s seen a gangster dressed up as a minister. Billy points them towards the Minister while Moonface Martin, who is wearing a minister’s robe, and Erma sneak onboard. They are on the lookout for Snake Eyes Johnson, a member of their gang and Public Enemy Number One. Immediately, they encounter the real Minister, who the FBI Agents mistake for Moonface because Billy points him out. As a reward, Moonface gives Snake Eyes’ passport to Billy so he can stay on the ship as Murray Hill Flowers. The Purser gives the final call: “All ashore that’s going ashore!” (Bon Voyage)
That evening, Reno spots Billy on deck. He confesses to her that he’s in love with Hope Harcourt, but she’s out of his league. Reno tries to bolster his confidence (You’re The Top). Billy encounters Hope, who informs him that no matter what feelings are between them, she must marry Evelyn. In Moonface’s cabin, the captain informs them that Murray Hill Flowers is actually Snake Eyes Johnson, still thinking that Moonface is a real minister. Moonface confesses to Billy that he is actually Public Enemy Number Thirteen — not a minister at all. Billy determines that he needs a disguise, and Erma sets out to get him a sailor suit. Later, on deck, a group of Sailors and Female Passengers sing together (There’ll Always Be a Lady Fair). Billy again tries to speak with Hope, but he is disguised as a sailor and gets pulled into a manhunt — for himself, since they think he is Snake Eyes Johnson. Reno recognizes Moonface Martin, and they team up in an effort to break Evelyn and Hope’s engagement (Friendship). While Mrs. Harcourt is frantically looking for her dog, Cheeky, Billy and Moonface enter in disguise and tell her that Lord Evelyn Oakleigh is an escapee from Bedlam who marries women and murder them. Mrs. Harcourt faints as Evelyn arrives on the scene, and Hope exposes Billy’s disguise. Reno encourages Hope to accept her true feelings as Billy re-enters disguised as an old lady (It’s De-Lovely). Just as Billy asks Hope to choose between Evelyn and him, the Captain and Deck Stewardess apprehend him, thinking he is Snake Eyes Johnson (Anything Goes). They are thrilled to have solved their celebrity problem, and Billy is named the honorary captain of the S.S. American (Public Enemy Number One).
Reno informs Billy that Hope wants to marry him just as the Angels and she head onstage for their next number (Blow, Gabriel. Blow). After the performance, Evelyn confesses his love to Reno, and Billy publicly confesses his love for Hope — at the same time outing himself as a phony gangster. Billy and Moonface are thrown into the brig (Be Like The Bluebird). Erma delivers a note from Hope to Billy — she loves him, but thinks there is no hope for them (All Through The Night). Luke and John are locked in the brig as well, and Reno confesses to Billy that she and Evelyn are in love with each other. Billy and Moonface win Luke and John’s clothes in a poker game, and they rush to stop the wedding. Billy claims that Evelyn owes a debt of honor to Plum Blossom, who is really Reno in disguise. Billy gets to marry Hope, Reno gets to marry Evelyn, Whitney steps in to marry Mrs. Harcourt and at the last moment, an urgent cable comes through from New York informing Whitney that Amalgamated shares — the same one Billy never sold off — have gone through the roof. The Captain marries all the couples, and all is well (Finale).