As Act I of the Titanic musical starts (Prologue) we find Thomas Andrews, the architect of the great ship, studying the blueprints of his great ship design (In Every Age). The curtain then rises on the dockside in Southampton, England, to reveal the ship. A growing collection of people are in awe of the sight. It is the day of the maiden sailing of the ship and representative characters start to board the ship: first a stoker (How Did They Build Titanic?), then other crewmen (There She Is), officers and stevedores (Loading Inventory), the owner, the architect and the captain (The Largest Moving Object), the 3rd and 2nd Class passengers (I Must Get On That Ship), and finally the 1st Class passengers (The 1st Class Roster). Once fully boarded, the ship sets sail as the company sings a prayerful farewell (Godspeed Titanic).
Some of the representative characters present their dreams and aspirations. Barrett, the stoker, wants to get away from the coal mines (Barrett's Song). Murdoch, the ship's officer, contemplates the responsibility of being in charge (To Be a Captain). Kate McGowan and the 3rd Class passengers yearn for a better life in America (Lady's Maid). The Chief Steward, Etches and the 1st Class passengers he serves, exult in the wonders of their world (What a Remarkable Age This Is!).
The scene changes to the Telegraph Room where Barrett is dictating a telegram of his proposal of marriage to his sweetheart back home (The Proposal). The young telegraph operator, Harold Bride, ponders the possibilities of the new wireless technology (The Night Was Alive).
After the Sunday morning church service, the following day, the 1st Class passengers are treated to a spirited rendition by the ship’s band of an alfresco dance/concert (Hymn/Doing the Latest Rag). Second Class passenger Alice Beane, wife to a hardware store owner, wants more out of her life and gate-crashes the event (I Have Danced). That same evening, as the lookout, Mr Fleet, scans the horizon for potential dangers (No Moon) one of the ships band members, Mr Hartley, entertains the 1st Class Smoking Room occupants with a song (Autumn). All the while the ship is heading towards her unavoidable collision with an iceberg, which brings Act I to an end.
Act II opens in the Grand Salon with the rudely awakened 1st and 2nd Class passengers assembling to be given lifebelt instructions from the Chief Steward, Mr Etches, (Dressed in Your Pyjamas in the Grand Salon) prior to going to the lifeboats on the Boat Deck. In the Telegraph Room Mr Bride tirelessly sends out SOS wireless messages, while Captain Smith, Mr Andrews, the architect, and Mr Ismay, the owner, argue over who is responsible for the impending disaster (The Blame).
Meanwhile up on the Boat Deck, women and children are given priority for places in the lifeboats over the male passengers (To the Lifeboats). But they all hope to be reunited later (We'll Meet Tomorrow). Ida Straus, the wife of Isador Straus, who owns the Macy's department store, refuses to leave his side after 40 years of marriage and they remain on the ship together (Still).
The Chief Steward, Mr Etches, utters a prayer (To Be a Captain reprise).
In the empty Smoking Room, Thomas Andrews, the architect, in a futile act, amends the blueprints of the ship to correct its fatal flaws as realisation suddenly dawns on him that the magnificent Titanic is doomed, just as the ship starts to sink (Mr. Andrews' Vision).
In an Epilogue, the survivors who have been picked up by the Carpathia retell Mr Andrews' dream (In Every Age reprise). A final tableau sees the living and their lost loved ones recapturing the optimism of the Southampton dockside on sailing day (Finale).