The Piano tells the story of Ada McGrath and her daughter Flora. Ada is a mute Scotswoman whose muteness is not caused by a medical condition but an unexplained psychological one that manifested itself when she was six and since then she has only communicated through her beloved piano, and also using sign language which is now interpreted by her daughter.. Ada's father sells her into a marriage with a cold and emotionally remote frontiersman in New Zealand, shipping both Ada and Flora to the other side of the world.
Ada is so wrapped up in her piano playing that she is almost oblivious to the rest of the world and had very little interest in. Ada, Flora and their belongings, including her piano, are dumped on a New Zealand beach by the crew of the ship they are travelling on and with nobody waiting to meet them find themselves spending the night on the beach sheltering beneath a tiny tent formed from the frame of a hoop skirt. In the morning, Ada's new husband Alisdair arrives with a Maori crew and his closest friend, Baines, who is an alarming looking man due to his embracing of the Maori custom of facial tattooing. There are not enough men to carry all of the belongings so despite Ada's pleas to the contrary the piano is left behind at the beach. Alastair tells Ada his house is too small to accommodate a piano, causing her to spend all of her time attempting to come up with a way to get her piano back, and making no effort to get to know him at all. As she cannot communicate with him she takes Flora to meet with Baines and begs to be taken to her piano. He agree, and the three spend the day at the beach listening to Ada play tunes. It is clear that Baines is attracted to Ada and it is her passion for music that is inspiring his passion for Ada. He decides to retrieve the piano himself and offers Alasdair some land that he wants in return for Ada giving him piano lessons. Alasdair is oblivious to his friend's attraction to his wife and agrees to the deal. Ada is happily surprised to find he had had the piano tuned perfectly since rescuing it from the beach and delighted to be playing it again, learning that Baines does not want her to teach him to play the piano but would like to listen to her whilst she plays. Baines devises a way in which Ada can earn the piano back, one key at a time, letting him do things he likes whilst she plays. Ada is attracted to Baines and agrees.
Ada's playing arouses Baines to such a degree that he approaches her openly in an effort to have sex with her; Ada cannot fight her desire for him and they make love. After learning from Flora that Baines listens to Ada playing but never has a lesson himself, Alasdsir finally realizes that there is an attraction between them. He discovers them together and boards up his home with Ada inside when he goes out to work on his timberland. Alasdair becomes angry when she pulls away from his touch. He elicits a promise from her not to visit with Baines whilst he is gone. She agrees but sends Flora to see Baines and deliver a piano key inscribed with a love message. Flora is unhappy about this infidelity and takes the key to him instead. Alisdair is so enraged that he returns home carrying an axe and chops off Ada's finger to deprive her of playing the piano.
After she recovers, Alisdair dissolves their marriage and both Ada and Flora are sent away, leaving from the same beach they had arrived onto. Whilst they are being rowed out to the ship Ada tells Baines to throw the piano overboard because she is doing it a disservice by being unable to play. He obliges, but as it sinks she loops the ropes attached to it around her foot and follows the piano underwater. As she sinks deeper and deeper Ada has a change of heart and kicks free so that she can be pulled back into the boat.
The movie ends with Ada describing her life with Baines in England, where she gives piano lessons thanks to a silver finger that has replaced the one Alisdair severed. We leave the film with the Thomas Hood quote from his poem "Silence" which also opened the first scene.
"There is a silence where hath been no sound. There is a silence where no sound may be in the cold grave under the deep, deep sea."