Vicki (Maureen O'Brien)
After leaving his Granddaughter on Earth, the Doctor, Ian and Barbara arrived on the planet Dido, in the 25th century. They discovered a crashed Earth space craft, with two survivors on board: a man named Bennett and a young girl, Vicki.
The Doctor discovered that Bennett had killed the other survivors, to cover up an earlier murder. When Bennett himself was killed, she elected to join the Doctor on his travels.
After several adventures (including the Doctor's first encounter with the Meddling Monk) Vicki fell in love with Troilus, in ancient Troy. There she left the TARDIS crew, and adopted a new name: Cressida.