Clint came from New Jersey. He had problems at home with his family and left his family to become successful in New York City.
He wanted to be an author and had started to write a book. In New York City Clint had to work as a cab driver. Clint did not have much friends in New York City. He regret to have left his family.
In 1965 Clint had dreames about being upducted by aliens. That was why he went to a psychiatrist, to tell him about the dreams. But it turned out that his psychiatrist was actually the Eleventh Doctor. Since the Doctor believed that what Clint had told him weren't dreams, he left together with Clint before the real psychiatrist Dr Bryson arrived.
The Doctor knew that the people in New York City had been poisened and wanted Clint to help him to find an cure. Clint was the only one who wasn't poisoned.
The Doctor found out that Clint was a control person for an alien experiment. Aliens wanted to create drugs for themselves. They wanted experiment on humans first before they use the drugs on themselves.
The poison turned out to be the drugs of the aliens, which they tested on the inhabitants of New York City. With the help of Clint the Doctor could convince the alien to give the cure to the people in New York City, who were all healed.