Oct. 25, 2013 -- intro: On Sept. 15, 2010, Greg Fleniken died unexpectedly in his hotel room in Beaumont, Texas.
There was no sign of a struggle, no obvious injuries to the body and nothing missing from the room. At first, police investigators believed Fleniken died of natural causes.
But a medical examiner ruled Fleniken's death a homicide.
Using photos from the scene of the crime, can you solve the mystery of how Greg Fleniken died?
quicklist: 1 category: Clues title: Clue No. 1: The Hotel url: text:Successful oilman Greg Fleniken often traveled to Texas on business from his home in Louisiana. A man of habit, he always stayed at the Elegante Hotel in Beaumont during his regular trips to the small town. media: 20672141
quicklist: 2 category: Clues title: Clue No. 2: Security Camera Video url: text: Footage from the hotel's security camera videos showed that Greg Fleniken entered the hotel at 5:03 p.m. on Sept. 15, 2010. media: 20673283
quicklist: 3 category: Clues title: Clue No. 3: Cigarettes, Cell Phone and Candy Bars url: text: According to those who knew him, Fleniken stuck to a routine at the Elegante Hotel. On his bed when he died were cigarettes, his cell phone and candy bars.
"He'd set up, and that was his routine for the evenings," Beaumont Police Detective Scott Apple told ABC News' "20/20."
"He had his phone to communicate with his wife or for business. He smoked a lot, and he had his candy bars because he had a sweet tooth." media: 20673228
quicklist: 4 category: Clues title: Clue No. 4: Broken Circuit Breaker url: text: With everything laid out on his bed, it appeared that Fleniken was settling in for the night.
He rented the movie "Iron Man 2" and microwaved popcorn. Because he was watching the movie and using the microwave, Fleniken blew out the circuit breaker and killed power to his room.
The circuit breaker was fixed by a hotel repairman, a registered sex offender. But the repairman had an air-tight alibi after he left Fleniken's room. media: 20672240
quicklist: 5 category: Clues title: Clue No. 5: Air Conditioner url: text: When the fuse blew in the hotel, the air conditioner in Fleniken's room had been turned off.
It was never turned on again, leaving the room very hot. According to private investigator Ken Brennan, who was hired by Fleniken's wife, Susie Fleniken, Fleniken "loved the room ice cold. His wife always said that; he liked it like a meat locker." media: 20672721
quicklist: 6 category: Clues title: Clue No. 6: Lit Cigarette url: text: The next morning, Sept.16, 2010, Fleniken was found lying dead on the floor of his hotel room between the bed and door. In his hand was a freshly lit cigarette.
Investigators noted that the cigarette was in Fleniken's left hand, even though he was right-handed. media: 20672647
quicklist: 7 category: Clues title: Clue No. 7: $1,000 url: text: Fleniken lived out of a suitcase when he stayed in Beaumont. His belongings, including more than $1,000, were left undisturbed in his room when he died. media: 20672622
quicklist: 8 category: Clues title: Clue No. 8: Autopsy Report url: text: The autopsy report said Fleniken suffered severe internal injuries, consistent with blunt force trauma. His body had broken ribs, lacerations to the liver and scrotum, and a hole in his heart. There was, however, no bruising or any other obvious signs of a beating. The medical examiner listed his manner of death as a homicide. media: 20672572
quicklist: 9 category: Clues title: Clue No. 9: Indent in the Wall url: text: Missed during the initial investigation was a small indent in the wall between rooms 348 and 349 that private investigator Brennan and Beaumont Police Detective Apple found later.
Maintenance records show the wall had been repaired, but the indent was still noticeable. The men staying in the room next door had been drinking heavily and told police they didn't have any idea what had happened. media: 20672499
quicklist: 10 category: Conclusion title: Solve the Mystery url: text: There's the evidence. Can you solve the mystery of how Greg Fleniken died? media: 20672141