San Diego — You've seen it on Hard Copy, read about it in the paper. Now, how about the truth on the millionairess, the parasite, and the million-dollar horse she claims was murdered, South Pacific?

Start with the basics: In Valley Center's rich farmland, a champion jumping stallion dies of one of the world's rarest diseases. Its distraught multimillionairess owner is convinced that her enemies injected a parasite to murder her horse. She puts out a $10,000 reward for information. She suspects it may be horse dealers hurt by the success of her bloodline, or perhaps developers fighting her campaign for water and wildland preservation in Orange County. She hires an ex-FBI private investigator. She establishes an 800-number telephone hotline. Even a mysterious expert from the U.S. military arrives to inspect her ranch and requests to be "kept informed."

Many say the champion jumper South Pacific was the love of Joan Irvine Smith's life. He was certainly the pride of her show-jumper stables. But she lavished care on him for good reason: the stallion made her reputation in the horse world.

Smith, great-granddaughter of James Irvine, the Scottish-Irish immigrant who created Orange County's 120,000-acre Irvine Ranch, is heiress to $350 million of the Irvine fortune. She owns three horse farms -- all known as "The Oaks" -- in Virginia, San Juan Capistrano, and Valley Center.

It was to the Oaks Indian Hill Ranch in Valley Center that Mrs. Smith retired South Pacific for breeding two years ago. The 43-acre spread, just beyond Bates Nut Farm, looks like a movie set, with horses nibbling at lush green pastures inside miles of wooden corrals surrounding a big red barn. More than a hundred horses have been retired here or were born here, the children of South Pacific.

Javier Moncada opens the door to stall number 28 in the barn, South Pacific's. Moncada's entire responsibility was South Pacific. Tears pool in his green eyes as he speaks. "He was my buddy for two years. He had great heart. He was the best horse I ever met."

We look down at the stall where the great horse was put to sleep April 15 at the age of 16. Black plastic covers white lime, spread to disinfect the stall. "I held his head for a day," says Moncada. "In the end, when he was blind and in pain, he would hit the door and neigh. The only thing that helped was when I put his forehead against the wall. He'd stand pressing that and pressing it..."

Vets discovered shortly before the great Holsteiner stallion was euthanized that tiny worms were eating out South Pacific's brain, eyes, and kidneys. The worm, Halicephalobus deletrix, kills horses and humans without mercy and without exception. Its life cycle remains a mystery to science. Apart from the 13 horses it has killed in the U.S. since 1985, it has also caused the death of two people on the East Coast and one Canadian boy. It is so rare, Mrs. Smith is convinced it was deliberately injected into her "flagship horse" by someone who knew the location of his unmarked stall.

Moncada shows some of South Pacific's 65 offspring in their stalls. Canaletto, Champagne, Esmeraldo, Cheer -- Holsteiners all. They may be stallions, but each is as loving and trusting as a child. "You see how easy they are to approach," says Moncada. "It would not have been difficult for someone with a needle. Till this happened we didn't even have locks on the stall doors."

To Moncada and Smith, the tragedy -- and the main cause of suspicion -- is that it happened to South Pacific. The seal-brown stallion was born in Germany in 1982 of royal lineage, combining the two legendary Grand Prix jumping bloodlines of Silbersee and Cor de la Brèyere. The Germans, it seems, have long held an edge on Holsteiner jumpers. South Pacific was brought to the U.S., where he made his name as a superb competitor.

Smith acquired him five years later and brought him to San Juan Capistrano. His success as a jumper was unquestioned, but it has been his later career, as a supplier of semen to mares, that gave him value beyond money. Smith's ambition was to beat the Germans at their own game, to breed horses that produced the perfect combination of "size, mind, and muscle."

Perhaps she was succeeding too well.

"When I entered South Pacific's stall on the morning of April 15," writes Smith in a tribute to her beloved stallion, "he was lying on the shavings with his head elevated. I called his name and he raised his head slightly and nickered softly in response. I told him we must say good-bye for now, but I knew we would meet again someday. His great heart never faltered until he was euthanized at 9:30 that morning. I remained beside him until his life drifted away."

I meet Joan Irvine Smith an hour north of Valley Center, at her home and second horse farm outside San Juan Capistrano. She's seeing off the Hard Copy television crew inquiring about the $10,000 reward she's offering for information about South Pacific's death.

Smith is a solid and commanding 65-year-old woman, smartly dressed in salmon-pink blazer and cream slacks. The salt and pepper of her straight, shoulder-length hair is highlighted by a gold chain around her neck joined by a gold belt buckle. Her slacks belt sports a brass horseshoe buckle.

Ocean I, a beautiful and successful son of South Pacific, comes out of his stall for exercise. Smith grabs some horse cookies from a bag and nuzzles them into Ocean I's mouth one at a time. Then she's off in her Range Rover with the breezy assurance of the rich.

"Talk with Bob," she says.

Bob McNeal is the private investigator she hired to find South Pacific's murderer. McNeal recently retired after 20 years as a special agent for the FBI. We sit down under the green canopy of fruitless mulberry trees.

I ask McNeal why somebody would kill South Pacific.

To find out, McNeal started by questioning the staff, including the two prime suspects: Moncada and Mrs. Smith herself. Moncada was always nearest South Pacific, and Mrs. Smith would stand to collect on the insurance. McNeal is sure Moncada is clear. But he had to confront Smith.

"I said, 'The first person anybody's going to consider is the one who has the insurance policy.' She said, 'I know that.' And she gave me the [insurance] documents. I didn't [suspect Mrs. Smith] because I hope that in 29 years I've gained some insight into people. Why would she hire me if there was any chance that I might find out she was the person that did this thing? Also, the insurance company didn't ever really question it."

McNeal feels that Smith's success as a late arrival to the world of horse competition and breeding could have generated enemies. "If you are interested in a world-class jumper, probably in the past you would have gone to Germany, paid what they wanted, and then had it shipped here. Now, you can come to San Juan Capistrano and get something of equal value. No shipping and customs fees. She told me this is the only horse that the Germans ever wanted to buy back. They offered $1.5 million. And she wasn't interested. We're talking possibly about people in the horse industry who view her as a real threat financially."

Then again, McNeal says he's also aware of people who resent Smith for supporting water conservation in developer-driven Orange County. "She's outspoken. She's third-generation Irvine. She's been married four times. She has three sons. And she's very involved with water. Maybe someone thought they could discourage her with this great loss."

If so, they got the wrong lady. That much is clear when Mrs. Smith finally returns. She believes she intercepted the perfect crime.

"If I hadn't ordered the biopsy and found out what the real cause was and then had the very expensive necropsy performed, we would have assumed he had renal failure from some reaction to [recent annual] inoculations. I think that was the intent. This was set up so it would appear that the horse died from an accidental death, so I would not investigate it."

"I'm a competitor to people who import [Holstein jumping] horses into this country for sale. I have never made a secret of the fact that the objective of this breeding program was to create an American sport horse that would be competitive with the European horses and would enable American buyers to buy horses in this country, rather than going abroad. I'm one of the first to do this on this scale."

She leads me over to the Range Rover. "And you want to know how easy it is to get these worms? Just go to the Internet. Type in 'Paul's Bizarre Worm Bazaar.' He's based in Belgium. Look! Here's how you order it."

She points to the Web site on a page she's printed off the Web. "Here is the selection of worms he has available."

Halicephalobus appears on a shopping list. "Most of these are freely available," writes the Web site's owner Paul de Ley. "Just send me a request by e-mail."

De Ley's only restrictions to anyone buying these deadly worms is they must include with their order a statement that the buyer is aware of the health risks, can handle and store the worms safely, and won't distribute them without warning the recipient.

"Yeah, right," says Smith.

But UCLA's Dr. Lawrence Ash, who's been a parasitologist for four decades, says the idea that someone could inject Halicephalobus and time its actions to be disguised by a vaccine is preposterous.

"That [idea] is so diabolically clever that I think Mrs. Smith should go into writing Sherlock Holmes-type novels."

Ash says that too little is known about this rare worm. "Even if you were [able] to culture them, I'm not certain [anyone would know when] they'd be at the appropriate infective stage for inoculating them. You could maybe give them a hypodermic needle into one of the veins and squirt in some of the worms, and maybe they would set up an infection. I don't know. Nobody, to the best of my knowledge, has ever been able to culture this and then use it experimentally to, say, infect mice or rats or hamsters, let alone horses."

Ash says a real worry is that larvae or eggs from the worm may still be in South Pacific's frozen semen, stored for future offspring of the dead horse. This semen is potentially worth millions, given South Pacific's record. If the semen is infected, it could spell disaster for Mrs. Smith.

"The first thing I would advise Mrs. Smith to do is [have] a parasitologist look at several of those [semen] straws, to see if he sees any worms. Are they indeed Halicephalobus? Will they be mobile when we thaw them out? Are they going to be infective or not? If I was the one inseminating my mares, I'd certainly think about it."

Back at the Valley Center farm, the sun is setting, turning the meadows luminous green. Smith's vet, Dr. Matt Matthews, here to check on a new foal, remembers something strange that happened soon after South Pacific died.

A military scientist from Camp Pendleton had heard how South Pacific died. "His name was Captain Hank Gardiner," says Matthews. "He toured the farm and left us phone numbers to call. In case we came across any other horse, they would like to 'take over' the situation.

"They were even talking about somebody donating a horse so they could inject the horse [with the worms]," says Nancy Lake, the farm's manager, who was also there.

"The military had some interest in the organism," says Matthews, "and we were concerned as to why." Matthews says visions of germ warfare immediately sprang to mind.

Captain Gardiner, when reached on the phone at Camp Pendleton, declined to comment. But First Lieutenant Tiley Nunnink in the public affairs office insisted that Gardiner's visit to the Oaks farm had "no ties to the military."

Ash confirmed that Gardiner is a well-respected parasitologist who has written papers on Halicephalobus. But Dr. Matthews is taking no chances. "I personally made a decision not to involve the [military]. I think the organism is too dangerous."