In 1953, a budding cricketer, Bob Blair, proposes to his girlfriend, Nerissa Love. However, the engagement is met with hostility from Nerissa's parents, who does not wish for their eldest daughter to marry outside their Catholic faith. Nerissa tries to solve the problem by getting Bob to convert to Catholicism, but Bob refuses, consequently ending their engagement. Trying to make it up to Nerissa, Bob buys her flowers and suggests getting married in a Methodist church (what he presumes to be neutral ground). Nerissa refuses and throws the flowers to the ground as Bob angrily walks off. She notices the gravestone next to her dedicated to a young wife who died at 21. Realising how short life is, Nerissa and Bob reconcile their engagement.
When Bob is selected to represent New Zealand in South Africa, he uses the money to buy Nerissa an egagement ring. Nerissa and Bob consumate their engagement when Nerissa's parents leave the town overnight. They are caught after the act by Nerissa's parents, who furiously banishes Bob from Nerissa's life. Knowing they will have little time together, Bob appeals to Nerissa's father, who becomes slightly more accepting. Before leaving the country, Nerissa and Bob share a tender moment, where Nerissa asks Bob to "hit a six for me".
As the days go by, Nerissa listens intently on the radio at Bob's progress. They send each other plenty of letters, but Nerissa still feels alone. Bob sends Nerissa flowers on Christmas Eve while still in South Africa, which catalyses a fight between Nerissa and her mother, who still refuses permission for Nerissa to marry Bob. Nerissa decides to run away from home and stay with her friends Eva and Jim in Auckland until she and Bob can get married. Nerissa catches the train that her friend, Toki, works on, and sneaks into first class with his help. On the train, Nerissa writes a letter to Bob stating that they will get married regardless of what others say. Toki send this letter off to the post office at their first stop.
That night, a giant wave of water hit and swept away one concrete support of the rail bridge at Tangiwai. The train continued onwards, and as the express left the bank, the rest of the bridge collapsed and the engine nose-dived off the edge into the air, almost hitting the opposite side. Nerissa's carriage plunged into the river, and water begins filling the inside. A window is smashed open and people begin climbing out. Toki frantically searches for Nerissa, but is dragged out before he can find her. Later in the carnage, Toki spots Nerissa's engagement ring and finds Nerissa's dead body in the wreck. He weeps and takes her to the emergency bay, where a nurse attempts to clean the mud off her face.
Stan and Eva hear about the accident on the radio, and realising Nerissa was on the train, notifies her father. Stan and Nerissa's father identify Nerissa's body. A telegram is sent to Bob notifying him of Nerissa's death, who withdraws from the match on the following day. Devastated by his loss, Bob stays in his room while his team mates face the South African team.
The NZ team is severely beaten by the South African team in the first inning, with Sutcliffe knocked unconscious and rushed to hospital. Sutcliffe collapsed twice, again at hospital but returned to the ground to resume the battle, re-entering the fray at six down. It was at about this point that Bob had heard enough on the hotel radio. Just as Sutcliffe was preparing to leave the grounds with one man down, Bob enters and shocks the audience. Sutcliffe went to his stricken team-mate and put an arm around his shoulders, saying "C'mon son, this is no place for you. Let's swing the bat at the ball and get out of here."
However, Bob continues. He wipes his teary eyes, and upon hearing Nerissa's voice asking him to "hit a six for me", swung the final ball of the over high over the midwicket boundary and into the terraces. As the crowd applauds, Bob sees a vision of Nerissa cheering him on.
The film ends stating that NZ went on to lose the test match against South Africa. Bob is shown receiving the final letter that Nerissa wrote to him before the Tangiwai disaster.