Mr. Reisner, a Jewish merchant, moves his family from their native Romania and establishes a successful business in Scotland. They move South to a town near London. On 31 December 1899, Mr.Reisner organises a party at his home to mark the new century, despite protests from his anti-Semitic neighbours, who argue that his celebrations are premature and should occur next year, at the dawn of 1901.

At the party, Mr. Reisner announces that his son Paul has gained a fellowship at a medical institute in London. The following day, Paul travels to London. He arrives at the institute a day early. He is shown his lodgings, which he will share with the other doctors. Paul meets the other researchers and is introduced to his laboratory space. That night he watches a couple making love in the next room.

Next morning, Paul is greeted by institute's head doctor, Professor Mandry. The doctors examine and treat a queue of sick patients. Paul strikes up an acquaintance with Clara, who works as a laboratory assistant at the institute. He questions one of the doctor's methods and a fight ensues. Mandry warns Paul over his behaviour. Paul invites Clara to dinner but she declines.

Paul arrives late for a meeting with Mrs. Whitweather, the institute's patron. She is concerned that animals are not experimented on. Mandry sees Paul's potential and suggests he accompany him to treat the sick people in a nearby slum. Paul visits a science exhibition with Felix and Clara.

Felix reveals an innovative research paper on insulin and diabetes. Paul and Felix take the proposal to Mandry, who initially seems interested, but the work is pushed to the background. A few days later, Paul is shocked to discover the papers languishing in a storeroom cupboard. He demands an explanation from Mandry, who refuses to discuss the subject and bans Paul from the institute for one month.

Paul seeks comfort with Clara and they make love. She reveals she once had a baby, which died young. Paul's father pays a surprise visit and demands a tour of the institute. Although he is banned from the building, Paul reluctantly shows him around. He unexpectedly runs into Mandry.

Mandry offers Paul a new chance at the institute on the condition that his work with Felix is not discussed. Paul accuses Mandry of professional jealousy. Mandry responds by informing him that he is finished at the institute and will never work in medicine again. Paul is approached by two policemen and questioned over his family's residential status. Paul suspects Mandry of arranging the disturbance.

Paul wishes to return to medical practice. Clara accompanies him to treat the sick in the slums. Paul is horrified to discover that Mandry has been using controversial methods to sterilise patients, without their consent. Some of the patients are dead.

Instead of confronting Mandry in person, Paul tells Mrs. Whitweather that the institute is using animals for research. The institute is closed down. Paul invites Felix and Clara to his father's New Year's Eve party. He discovers that Mandry has also accepted his father's invitation to the celebration.

At the party, Paul discovers that his father is moving, due to the intolerant local community and his ailing business. Paul confronts Mandry and orders him to leave the party. Mandry asks him to retract his statement so funds can return to the institute, then leaves. Paul asks Clara to marry him at the chimes of midnight.

Many years later. Paul recalls that his father lived for another twenty years, while Felix continued with his work on diabetes. Paul wonders how different it could have been if Mandry had supported their earlier work. Mandry is no longer a doctor and is rumoured to have committed suicide. Paul and Clara never married but remain together. He reminisces over the night that heralded the turn of the century, recalling the feelings of excitement and trepidation for what the future would hold.