The First Doctor was the first incarnation of the Time Lord known as the Doctor. Most accounts of him were drawn from close to the end of his life.
Initially, he had as companions his granddaughter Susan Foreman and her kidnapped teachers, Ian Chesterton and Barbara Wright. He bade Susan farewell to let her live a happier life with a man with whom she had fallen in love. Later, during a confrontation with the Daleks, the Doctor used one of their time capsules to return Ian and Barbara to their proper time - something he had been unable to manage with the TARDIS.
After Susan's departure, the Doctor gained a new companion in Vicki Pallister. She reminded him of Susan and the Doctor saw her as a surrogate to fill her spot in his travels with Ian and Barbara. Vicki left the Doctor's company, feeling her time with him was over and she needed to move on.
Soon after the departure of Ian and Barbara, the Doctor gained a new companion in Steven Taylor, with whom he had a relatively uneasy relationship. Steven was bitter towards him, blaming him for the deaths of Katarina and Sara Kingdom. However, the Doctor was forgiven and companion Dodo Chaplet joined them on their travels.
Ultimately, Dodo became injured in an adventure and decided to remain home in her own time, while Steven decided to stay and help a civilisation they had encountered.
Right before his battle with the Cybermen of Mondas, the Doctor had gained two new companions in Ben Jackson and Polly Wright, to whom he was much more kind to prevent them from leaving as Steven had.
He met his end after battling the Cybermen for the first time on Earth. He was forced to regenerate into his second body from exhaustion and a loss of strength to maintain his ancient body.