Sisters of PlenitudeThe Sisters of Plenitude were first seen in New Earth (Series 2 : Episode 1) as an order of Catkind nuns. They worshipped the goddess Santori and devoted their lives to healing the sick, though they were ready to use violence to defend themselves. A group of these sisters ran the hospital just outside of New New York on New Earth. The Sisters were able to treat diseases with amazing efficiency, and with treatments that should not have been available for at least a thousand years, according to the Doctor.
The Cat Humanoid beings are referred to as Cat People, and are able to mate with humans, producing offspring as seen in Gridlock (Series 3 : Episode 3). The Sisters evolved their techniques for curing diseases brought to New Earth by the humans by growing their own human clones and experimenting on them. The clones were infected with every disease known to the Sisters as more humane methods were deemed to be too slow to deal with the diseases. The clones were killed if they began signs of thought as curing them would have taken too long to let them live. The disease carrying clones were released by Cassandra and eventually cured by the Doctor when he mixed a cocktail of medicines.
The Sisters attempted to stop Cassandra and the Doctor, but Matron Clasp, the Sister in charge, was killed when she was infected by one of the diseased clones. The rest of the Sisters were arrested by the NNYPD (New New York Police Department) for experimenting and testing on humans. Novice Hame, a Sister who had been looking after the Face of Boe in Ward 26, was seen again in Gridlock to be continuing the care of the Face of Boe. The Doctor reckoned that Novice Hame had reformed since her arrest for the cloned humans and wept when the Face of Boe died. Novice Hame showed that not all of the Cat People were enemies of the Doctor, as did others within the Gridlock episode.