Sheila Parker aka Laura Masters (Caroline Langrishe) is a villainess from "An Unholy Death", episode 2.02 of BBC's Death in Paradise (airdate January 15, 2013). Sheila was a former cancer nurse in Sussox before fleeing the country after killing one of her wealthy patients with a fatal injection, leaving her to inherit his money.
Sheila later took on the name Laura Masters and began a relationship with Daryl Dexter, the head of a PR firm, eventually becoming engaged to him. Prior to the episode's events, Sheila colluded with Daryl to claim the spring near Le Couvent du Sacre-Coeur (Convent of the Sacred Heart) was healing holy water, with the rumor being aided by Sister Anne believing the water had healed her of her cancer.
When Anne's cancer resurfaced, however, Sheila helped keep the revelation covered up by secretly going to the convent to administer Anne's treatments, disguising herself as a nun to sneak in, with Daryl also paying people off to claim the spring water had cured them as well. When nun Therese was found murdered in the convent, Sheila was questioned by DIs Richard Poole and Camille Bordey after they discovered the scam involving the spring. During the interrogation, however, Sheila denied her husband bribing anyone and claimed that she and her husband were together at the time of Therese's murder. But later on, Sheila was caught sneaking onto the convent by Officer Dwayne Myers, revealing her as the "Phantom Nun" and exposing her complicity in the spring scam.
Sheila was later questioned by Richard and Camille with Daryl present, with the detectives having uncovered Sheila's true identity and how she had killed a patient and inherited his money. Sheila attempted to justify her crime, claiming the man was dying of stomach cancer and asked her to put him out of his misery (with Richard disbelieving her claims). Daryl also revealed that Sheila had lied about them being together during Therese's murder, leading Sheila to become a suspect in the case. Ultimately, though, Sheila and Daryl were proven innocent when Anne was revealed as Therese's killer, and Richard and Camille were unable to arrest the couple for their villainous fraud due to a lack of evidence.