Abigail Pettigrew

Abigail Pettigrew, the sister of Isabella, was one of the people taken by Elliot Sardick as "security".

Frozen
Abigail was cryogenically frozen by Elliot Sardick against a loan of thirty-five hundred gideons to her family. This sort of "security" allowed him power over those who owed him money. Abigail suffered from a fatal disease; the freezing prevented her death but when she awoke her condition deteriorated again. A counter placed on the outside of her freezing chamber kept count of the time she had left to live if unfrozen.

Christmas adventures
Abigail was awoken by Kazran Sardick and the Eleventh Doctor. She was able to calm a sky shark hunting them by singing to it. She went with them in the TARDIS to return the shark to the cloud bank. Abigail then returned to her case. Just before she froze, Kazran promised they would visit each year.

Kazran and the Doctor woke her every Christmas Eve and took her places. Over the years as he grew older, she and Kazran fell in love.

She did this for as long as she could, but when she only had one day left to live unfrozen, she told only Kazran of her illness. She returned to her case. A thoroughly heartbroken Kazran told the Doctor only that he did not want him to return next year as the annual outings had gotten "old".

Final day
Many years passed and Abigail remained frozen. A spacecraft was damaged in the cloud bank on Christmas day, and was about to crash. The Doctor needed Abigail to sing, which would break up the cloud and allow a landing. Kazran was reluctant; he had been unable to choose what day should be their last together. Having awoken and heard the question, Abigail exited the stasis pod and told him "Christmas day".

She sang into the Doctor's sonic screwdriver. This was transmitted to its other half in the shark. The cloud opened and the ship survived. Kazran and Abigail spent her last day together, using the shark to fly across the sky in a carriage as they had in one of their first adventures with the Doctor. (TV: A Christmas Carol)

Personality
Abigail had a sweet, affectionate and kind-hearted personality. She was an extremely good singer and was able to easily calm even the sky sharks. Abigail was optimistic, even though she knew she was dying, and was determined to enjoy the time she had left. She fell in love with Kazran Sardick and although she teased him about waiting so long to release her from cryogenic suspension and growing into an elderly man, she did so affectionately and still loved him, choosing to spend her last few hours with him.

Behind the scenes

 * Unlike other one-off characters appearing in recent specials, Abigail was never promoted by the BBC as being a "companion" of the Doctor. Ironically, however, she and Kazran are in fact the first "one-offs" since Donna Noble in The Runaway Bride to travel through time and space in the TARDIS, fulfilling a generally accepted criterion for being a companion.