McArthur was last seen in Worcester, Massachusetts on September 14, 1982. That day, his daughter took a phone message from him while he was out. The caller said he should go to the Italian Kitchen on Shrewsbury Street. McArthur went to the restaurant after he got the message and never returned. Police later learned three men escorted him out of the restaurant. He has never been heard from again. Two weeks after his disappearance, his maroon Ford Thunderbird was found on the outskirts of the Combat Zone in Boston, with two weeks' worth of parking tickets on the windshield. McArthur's leather jacket and cigarettes were inside, but there was no indication of his whereabouts.

McArthur was allegedly involved with drugs at the time of his disappearance. He had appeared troubled and broke down in tears shortly before he went missing, but he refused to tell his wife what was bothering him. At the time of his disappearance, he was married, had two children and worked as a supervisor at the Harrington & Richardson firearms company in Gardner, Massachusetts. He was having an affair with a coworker.

Authorities believe McArthur was murdered by multiple individuals. The prime suspect in his case is still alive and living outside the United States, but others who may have been involved have died. Investigators searched several bodies of water, including Lake Quinsigamond, for McArthur's body, but never located any evidence. He was declared legally dead seven years after his disappearance. Foul play is suspected in his case, which remains unsolved.