The mysterious companion of Gary Seven who usually appears as a black cat but can take the form of a woman.
Isis accompanies Gary Seven, the human agent raised by an unseen alien power, on his mission to Earth in 1968 in Assignment: Earth. She appears for most of the episode as a sleek black cat wearing a jewelled collar, able to understand far more than an ordinary animal.
Isis helps Seven at key moments, and at one point she briefly appears to Seven as a dark-haired woman, a glimpse of a nature never explained. She remains with him on Earth after the mission.