A French nanny was beaten, mistreated and thrown on a bonfire after becoming "trapped in a domestic nightmare", a court has heard.
"Big hearted" Sophie Lionnet, 21, was killed after she went to live with mother-of-two Sabrina Kouider and Ouissem Medouni, the Old Bailey heard.
The pair allegedly confronted Miss Lionnet with "outlandish" allegations and kept her a prisoner in their home in Wimbledon, south-west London.
Prosecutor Richard Horwell QC told jurors: "Sophie was trapped in a domestic nightmare."
Kouider, 35, the former partner of original Boyzone band member Mark Walton, and Medouni, 40, have denied her murder in September last year.
The court heard Kouider accused her nanny of being "in league" with Mr Walton and in rambling complaints said he controlled her through "black magic".
Mr Walton has categorically denied her allegations against him.
Opening the Old Bailey trial, Mr Horwell told how Miss Lionnet had gone to live with the couple shortly after her 20th birthday.
He said: "Sophie was not only young, but also, we suggest, naive and particularly vulnerable and this made her an easy target for abuse and exploitation.
"The life she led in Wimbledon was at times bizarre and oppressive: it appears, for example, that she was hardly paid for her work as a nanny, but Sophie thought that that was acceptable because she believed that Sabrina Kouider could not afford to pay her.
"Sophie had a big heart but was not worldly wise and it was easy to take advantage of her."
She complained she was being beaten and not allowed to return to her home in France, jurors were told.
Kouider would shout and scream at Miss Lionnet and made a series of false allegations against her, accusing her of stealing a diamond pendant, the court heard.
Mr Horwell told jurors the false accusations were "contagious" and Medouni was "beguiled" into taking on the delusions.
He told jurors Miss Lionnet must have been "terrified" but lacked the strength to walk out, even as she became "emaciated".
Mr Horwell said: "The last days and hours of Sophie's life must have been truly wretched.
"She was subjected, at times, to a brutal and oppressive inquisition and to significant violence."
Miss Lionnet suffered fractures to her sternum, ribs and jawbone, but the exact cause of her death was unknown due to an attempt to dispose of her body, the court heard.
The barrister said: "The defendants burnt her body in the garden of their home in the hope that no-one would ever discover her remains.
"Their plan was to dispose of Sophie's body and to explain her disappearance by inventing a story that she had left their employment under something of a cloud.
"But their wicked plan was frustrated by the combination of a neighbour and inquisitive firefighters."
Following her death, more than eight hours of "harrowing" recordings were recovered from the defendants' mobile phones of Miss Lionnet being interrogated, the court heard.
Mr Horwell said they depicted "a young emaciated, frightened and helpless woman".