A 42-year-old woman and her live-in partner were arrested on Wednesday for allegedly killing an elderly couple and their nursing attendant in southwest Delhi's Vasant Vihar area, police said.
Preeti Sehrawat and Manoj Bhat (39) were nabbed from Gurugram, they said.
The bodies of the elderly couple, Vishnu Mathur (78) and Shashi Mathur (75), and their nursing attendant, Khushbu Nautiyal (24), were found with their throats slit on Sunday morning.
According to police, the accused duo knew the family and Preeti was a close family friend of the couple. Her father was also a colleague of one of the deceased.
They were killed with an intention of robbery, a senior police officer said.
Earlier, police suspected that the killings were executed by someone close to the nursing attendant and had ruled out the robbery bid.
However, interrogation of the accused duo revealed that the killings were executed to rob the Mathurs.
Further investigation is under way, police said.