A five-year-old boy, A. Periyasamy, was reportedly beaten to death at Pushpathur village near Palani on Wednesday.
Alerted by the local people, police found the body of the boy with deep injuries lying in his house. They sent the body to Palani Government Hospital for post-mortem.
After preliminary investigation, the police suspected that an illicit relationship between his mother Marikannu and a man at Neikarapatti could be a reason for the murder of the boy. Marikannu (38) was arrested.
Swaminathapuram police have registered a case and are investigating.