Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

At a lab near Hannover, Germany, scientists are studying human bones for clues to a 322-year-old missing persons case. And not just any missing persons case — at the center is a king of England, the wife he locked up for 30 years and her lover, a handsome Swedish count who disappeared in 1694.

Construction workers discovered the remains while renovating Leine Castle in Hannover, the former seat of the Hannoverian kings and home to Duke Georg Ludwig of Brunswick-Lüneburg — later King George I of England — and his wife, Sophia Dorothea, in the 17th and early 18th centuries.

Sophia Dorothea was just 16 when she married her cousin, the future king, in 1682. It was an arranged marriage and an unhappy one. Georg ignored his wife, preferring to spend time with his mistresses, so Sophia turned to Count Philipp Christoph von Königsmarck for affection.

Sophia Dorothea, the wife of King George I of England, and her lover, Count Philipp Christoph von K?nigsmarck, whose bones may have been found in an old German castle.

Three hundred of the letters still exist, held at Lund University in Sweden, which provided NBC News with access to them.

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

"Of course it was dangerous," said Håkan Håkansson, an associate professor of the history of ideas and science at Lund University. "It all ended badly, but I suppose they had persons they trusted who delivered the mail to each other."

In the summer of 1694, the pair agreed to run away together. But their secret was discovered, and after a late-night rendezvous, Count Philipp disappeared.

Royal rumors spread that the count was murdered on the orders of the vengeful Duke Georg, his body thrown in the river or buried in the castle walls. A body was never found.

Georg divorced Sophia Dorothea and locked her away in the Castle of Ahlden for the rest of her life. She was 28 years old, and for 30 years, she was held prisoner, separated from her children.

In 1714, Georg became King George I of England. His coronation was not well received — his subjects viewed him as a German invader who refused to learn English.

IMAGE: King George I of England.

"George I was not a likeable man. He was distant. He was cold. He was often cruel," said Professor Kate Williams, a specialist in royal history at the University of Reading in England.

"Certainly, there was a lot of gossip saying he did it, [that] he had it ordered," Williams said. "It was on his behalf that is was ordered, and it seems very likely it could have been so."

But is there any proof?

Scientists examining the bones weren't able to determine cause of death.

"Most of the bones were broken ... and not very well preserved," said Birgit Gorsskopf, an anthropologist at the University of Göttingen.

But the remains, which were found under the castle, yielded DNA that could be tested against the count's living descendants.

If the tests pan out, they it could provide the first answer in centuries to a secret a king may have taken to the grave.