Doctor Who question?!

Doctor Who question?

Which episode of the earlier Doctors (1-8) features the Doctor traveling alone without a companion?

Thanks.

"The Deadly Assassin." The Doctor leaves Sarah Jane behind at the end of the previous serial, "The Hand of Fear," when he is recalled to Gallifrey to tend to an emergency. He doesn't pick up a new companion until the serial following "The Deadly Assassin," "The Face of Evil."