In the next serial , Robot , after the Doctor 's third regeneration , Sullivan is called in to attend him , and ends up traveling aboard the TARDIS with the Fourth Doctor and Sarah Jane Smith ( played by Elisabeth Sladen ) for several subsequent adventures .
In the next serial , Robot , after the Doctor 's third regeneration , Sullivan is called in to help him , and ends up traveling aboard the TARDIS with the Fourth Doctor and Sarah-Jane Smith ( played by Elisabeth Sladen ) for several adventures .