Following the departure of Liz Shaw, The Doctor was temporarily without an assistant until The Brigadier assigned UNIT’s new recruit Josephine Grant to him. Initially the two did not get on but with the arrival of The Master and the initiation of his plans to conquer the earth, the two became firm friends and a force to be reckoned with, as they fought back many of The Master's schemes as well as attacks from extra-terrestrial threats that included The Daleks, she would even meet the Doctors previous two incarnations and help save Gallifrey itself from the Time Lord Omega.
As well as alien threats Jo would also encounter the Sea Devils and would travel to another planet when The Doctor made a ‘test flight’ to Peladon. During an investigation in Wales Jo would meet a young professor and decide to leave UNIT and The Doctor, it would be many years before they would meet again.
In contrast to several previous companions of the Doctor, Jo had limited training in science. She had once attempted to study for an A-level (Advanced level) certificate in general science. She failed to graduate and was only hired by Unit due to an uncle pulling some strings for her.
She substituted academic skills with enthusiasm, determination, and a talent for physical and mechanical skills. She demonstrated skills at martial arts, lock-picking, driving motorbikes, and piloting helicopters.