Florence Finnegan

"Florence Finnegan" was the alias assumed by a Plasmavore criminal hiding on the planet Earth from the Judoon and masquerading as a human.

Like other Plasmavores, she subsisted on blood for nourishment. She fled to Earth to escape capture by authorities, and had the ability to change her internal physiology to match that of native life forms if she had also absorbed their blood.

Checking into Royal Hope Hospital, Florence claimed to be overcome with dizziness. Julia Swales suggested that they do a CT scan or some blood tests, but Dr. Stoker said that she was simply salt-deficient as she had only eaten salad over the previous days. It was actually the case that, being a Plasmavore, she absorbed salt very well. She commanded two Slabs, one of which was killed by the Tenth Doctor and the other by the Judoon. She also owned a stripy red-and-white straw with which to suck her victims' blood.

Her victims included the Child Princess of Padrivole Regency 9 (whom she killed on a whim) and Dr B. Stoker, a doctor at the Royal Hope Hospital, whom she killed to assimilate his blood so she would appear biologically human to the Judoon scanners. She also drained the Doctor of blood, and in so doing nearly killed him. However, this enabled the Judoon to recognise her as not human, and therefore the fugitive that they had to capture/execute. The Judoon ultimately decided to kill her with their pistols, but not before she activated the MRI. (TV: Smith and Jones)

Alternative timeline
In an alternative timeline accidentally created by Donna Noble, the Doctor died on Christmas Eve 2007 along with the Empress of the Racnoss and was consequently dead by the time that the Judoon transported Royal Hope Hospital to the Moon.

In the Doctor's subsequent absence from the timeline, Sarah Jane Smith defeated Finnegan with the assistance of Martha Jones, Clyde Langer and Maria Jackson. In spite of their efforts, they and everyone else in the building died of oxygen starvation save for Oliver Morgenstern. Martha had given up the last of her own oxygen to save him. (TV: Turn Left)