A 29-year-old man was arrested over the alleged murder of an elderly couple in northeast Delhi's Gokalpuri, police said on Thursday. The couple was found dead at their residence on Monday with their throats slit, following which their daughter-in-law Monika Verma was arrested for allegedly killing them with the help of her boyfriend Ashish Bhargav and his associate, according to police. Bhargav, a resident of Ghaziabad, was arrested Wednesday evening from the NCR city, they said.