Dr. Martha Jones (later Martha Smith-Jones after marrying Mickey Smith) was a British freelance alien hunter who began her career as a medical student before becoming a companion to the Tenth Doctor and later a medical officer with UNIT. She was also attached briefly to Torchwood 3.
In 2008, Martha was working at the Royal Hope Hospital when it was transported to the Moon by the Judoon. Calm while those around her panicked, Martha worked with the Tenth Doctor, posing as a patient named John Smith, to track down the Plasmavore, "Florence Finnegan", the Judoon were searching for.
As the oxygen in the hospital ran out, Martha gave her last breaths to resuscitate the unconscious Doctor, who had thwarted Florence's plan. The Judoon returned the hospital to Earth. That evening, a recovered Martha was approached by the Doctor, who revealed that he was a Time Lord and invited her to join him on a trip through time and space in the TARDIS.
Martha was a friendly, intelligent, brave and good-spirited woman. When she was a prisoner of the Daleks, one of them confirmed that she possessed high intelligence. The Doctor was impressed with her theory about having air on the Moon, and he asked her to join him in the hospital balcony to see if they could breathe. Although the Doctor asked more of her than any other companion (watching after him while he was human, walking the world for a year), she rose to every challenge.
Martha quickly developed a crush on the Doctor and always wondered if he even noticed her. Martha was envious of Joan Redfern when the Doctor made himself human and fell in love with her, and said he "had to go and fall in love with a human, and it wasn't me".
In The Year That Never Was, Martha admitted that she loved the Doctor, but after the Master's defeat, she decided that holding on to the hope that he would return her feelings was not good for her. She was later engaged to Tom, and for unexplained reasons married Mickey Smith instead.
Although she had cause to be jealous of Rose Tyler, Martha seemed genuinely happy for the Doctor when he and Rose were reunited. She got along very well with Donna Noble. Martha also had a good relationship with Captain Jack Harkness and did not mind when he flirted with her.
