[17] Vastra is a female Silurian warrior from Mesozoic Earth who was awakened from hibernation in the Victorian era when her lair was disturbed during the construction of the London Underground.

Jenny's backstory in "The Battle of Demons Run: Two Days Later" (2013) shows she was turned away from her family because of her "preferences in companionship",[10] and saved from attackers by Vastra, who took her on as an employee.

In their first appearance in "A Good Man Goes to War", the three, along with others who owe him favours, are chosen by the Eleventh Doctor to help him save Amy Pond from Madame Kovarian and the Order of the Headless Monks at Demons Run.

They fight together against their enemies and succeed in saving Amy, but Strax is mortally wounded and appears to die after saying his last words to Rory Williams.

They then appear in "The Snowmen" (2012), trying to convince the Eleventh Doctor to come out of retirement (into which he has retreated after losing Amy and Rory in "The Angels Take Manhattan").

[1] The trio — and more particularly Jenny — have a central role in the first half of "The Crimson Horror" (2013), set in 1893, in which they investigate a series of strange deaths.

She finds the Eleventh Doctor, kept prisoner in Sweetville, and the trio reunites to help him defeat Mrs Gillyflower, by sabotaging the rocket she was planning to use to poison the skies.

[2] The three characters reappear in the seventh series finale "The Name of the Doctor", where they organise a meeting in a dream with Clara and River Song.

During the "conference call", the three are captured by the Whisper Men, minions of the Great Intelligence, who uses them as bait to bring the Eleventh Doctor to his tomb on the planet Trenzalore.

After Clara enters the timestream to save the Doctor and undo the Great Intelligence's changes to history, Jenny and Strax are restored.

[19] In "Deep Breath", the first episode of the eighth series, Vastra, Jenny, and Strax arrive in central London to witness a dinosaur marching through the city and proceeding to cough up the TARDIS.

McIntosh previously appeared in the series portraying two other Silurian female characters, sisters Alaya and Restac, in the two-part story "The Hungry Earth"/"Cold Blood" (2010).

[3] In an interview in the Doctor Who Magazine issue dated April 2015, Steven Moffat said that the BBC suggested a spin-off series about the characters,[33] but he rejected the idea due to his other commitments.

[additional citation(s) needed] The three characters have met with positive reviews from critics who praised their chemistry, as well as the humour concerning Strax and his Sontaran warrior habits, often at odds with the context.

He also stated "with marriage equality so much on the agenda, the divine Vastra and Jenny can only be a good thing to have on screens at tea time.