(CNN) -- It has all the trappings of a proper murder mystery: an attractive, up-and-coming victim, a sudden death, a mysterious stranger, whispers of poison.
Only this case involves a dog, the highly competitive canine show circuit and a professionally adorable Samoyed named GCH CH Polar Mist Cruz'n T'party At Zamosky -- Cruz for short.
The 3-year-old dog fell ill and died on February 16 in Lakewood, Colorado, barely a week after he appeared -- but didn't place -- in the prestigious Westminster dog show.
"I think somebody deliberately poisoned this dog," Cruz's handler, Robert Chaffin, told CNN on Friday.
But, as with any good mystery, it's not that cut and dried.
The profuse bleeding that killed Cruz can be caused by a number of conditions, according to the veterinarian who examined Cruz, Molly Comiskey. After Chaffin rushed the dog to the vet when he threw up blood, Cruz owner Lynnette Blue says, Comiskey listed rat poison as a possible cause.
But because Chaffin and Blue declined a necropsy or further testing, the final answer won't ever be known, Comiskey said in a statement.
Blue says Comiskey told her a necropsy wouldn't have shown anything if the dog had been poisoned days before. The few she's allowed before all turned up inconclusive, she said.
"Also, the thought at the time of him being cut open was too much for me," Blue said.
Westminster dismissed the poisoning suggestion, saying no other dogs fell ill at the show.
"We have never, to our knowledge, had an incident at our show where a dog has become ill or was harmed as a result of being poisoned," the group said in a statement this week.
But the sudden death of an otherwise healthy, closely watched dog seems to point toward poisoning, Chaffin and Blue say.
Chaffin says he watched Cruz closely to make sure he didn't get into anything dangerous. The trip to New York was uneventful. He and Cruz dined on steak from a Manhattan restaurant the night before the show. He scoured their hotel room for no-nos.
And they traveled together to Colorado, where he was appearing in the Rocky Mountain Classic dog show.
The only unusual thing happened during the Westminster show, when a "scowling" woman emerged from the crowd and accused him of being "cruel" and a "horrible person."
The Westminster show has been "plagued by activists" upset with the dog show circuit, Chaffin said. Among other things, people have been upset about a procedure called bark reduction, in which a dog's vocal cords are modified to make it quieter. Cruz had the procedure, Chaffin said.
But he wouldn't go so far as to implicate activists -- or the mysterious, angry stranger -- in Cruz's death.
"I don't know who it was. I think it was done by someone who was sick," he said.
It certainly wasn't us, said Lisa Lange, senior vice president of communications for People for the Ethical Treatment of Animals.
"It's absolutely outrageous. The people who should be charged with cruelty to animals in this case are the owners for having cut the vocal cords of this poor dog because they didn't want to hear him bark," she said. "And unfortunately, this is not unique to these people. In the really creepy world of dog shows, animals are having their vocal cords cut, their ears cut, their tails are cut off, to make them look a certain way so that their owners can become famous or make money. And it's just sick and it's perverse, and of course it's cruel."
With so much uncertainty, Blue says, the mystery will probably never be solved.
Whatever happened to Cruz, Chaffin and Blue are mourning the loss of the fluffy white dog, who was named best in breed at recent shows in Louisiana and California, and won best in show at contests in Mississippi this year and Louisiana and Texas last year, according to the website doggiestats.com.
"I just can't seem to stop crying and can hardly see," Blue wrote on her Facebook page.
CNN's Ashley Fantz contributed to this report.