The heart of the 10-year-old heir to France's throne was cut from his body when he died in prison, pickled, stolen and returned -- and DNA-tested two centuries later.

This week, Louis XVII's heart will be placed in France's royal crypt north of Paris now that genetic testing has persuaded many historians that the tiny petrified heart is almost certainly the real thing.

In ceremonies on Monday and Tuesday, European royalty will honor the little boy who became a pawn of the French Revolution, dying alone in a filthy prison. After a Mass on Tuesday, his heart will be laid to rest at the Basilica of St. Denis near the graves of his parents, Marie Antoinette and Louis XVI.

The ceremonies recognizing the royal heart seek to close 209 years of rumor, legend and historical uncertainty surrounding the child's death -- though some skeptics still insist the mystery has not been solved. Many historians had insisted that the true heir escaped and the sickly boy who died was a substitute.

"I would have liked to believe the story that the child survived," Prince Charles-Emmanuel de Bourbon de Parme, one of Louis XVII's closest living descendants, said at a news conference. "Today, science has proved the contrary."

Louis XVII's short life was the stuff of nightmares. He lost his parents to the guillotine. He was locked in Paris's Temple prison for three years -- for part of that time, in solitary confinement in a darkened cell, without anyone to wash him or clean up after him, said historian Philippe Delorme.

The boy finally died of tuberculosis in 1795, his body reportedly ravaged by tumors and scabies.

The child's corpse was dumped in a common grave -- but first, a doctor secretly carved out his heart, in keeping with a tradition of preserving the hearts of royalty separate from their bodies. The doctor smuggled it away in a handkerchief and kept it as a curiosity, Delorme said in a telephone interview.

Instantly, rumors spread that the true heir had been spirited away from the prison, with a commoner left in his place.

"It's a universal myth, the myth of the lost or hidden king," said Delorme, whose research about Louis XVII led him to organize the DNA tests in 2000. "In all civilizations, in all eras, there is this myth of people who have been hidden from us."

After the restoration of France's monarchy in 1814, about 100 people claimed to be Louis XVII, in places as far-flung as the Seychelles, Delorme said. Even a Wisconsin missionary who was part Native American claimed to have been the "lost dauphin," as Louis XVII was often called.

In France, the doctor who had cut out the heart kept the organ on a shelf in a crystal vase filled with alcohol -- a tantalizing souvenir for one of his students, who stole it.

Repenting on his deathbed, the thief asked his wife to give it back.

After the restoration, the heart was offered to various members of the royal family, and finally found its way to the Spanish branch of the Bourbons.

They returned it to Paris in 1975, and it has been held since at the Basilica of St. Denis. But it was recognized merely as the heart of the child who died in the prison -- not necessarily that of the royal heir.

Before the genetic tests, many people simply couldn't believe the royal heart could have survived 200 years passing from person to person.

But when scientists at two European universities compared DNA from the heart of the dead boy to DNA from hair trimmed from Marie Antoinette during her childhood in Austria, the link was confirmed.

The results left a few lingering skeptics to retort that the heart could have come from Louis XVII's brother, who died in 1789. Historians don't think so because that heart would have been cut and preserved according to strict royal tradition.

There will always be doubters. Louis XVII's story "was so horrible, and people preferred a happy ending," said Delorme.

"He was a child whose life was stolen from him. Even his death was stolen from him," Delorme said. "People just couldn't admit that he truly died in such awful conditions . . . . In the end, it is a wound in the history of France."