- [Narrator] Human remains.

A sealed lead sarcophagus of unknown age.

Finding bodies is not completely unexpected.

Burials in and around the cathedral are part of its history, but a sarcophagus like this one is very rare and immediately begs the questions, "Whose remains are these" and "Why are they here?"

This coffin is full of unexpected discoveries.

His remains will be the subject of a much more detailed analysis.

By collecting enamel from the teeth and a few grams of bone from a fingertip, it is possible to find clues to where he grew up.

It's called isotopic analysis.

Our bodies are made from the carbon and other chemical elements we take in when we eat and breathe.

Among the atoms of those elements, there are variations called isotopes.

The isotopes of strontium, oxygen and sulfur can point to the geographical location where someone grew up.

And nitrogen and carbon can help determine if he ate mostly fish or meat throughout his life.

Anthropologist, Rozenn Colleter and geochemistry researcher, Klervia Jaouen, process the samples of enamel and bone collected from the remains.

In order to extract the chemical isotopes that will tell the story of where he lived, they first soak the samples in an acid bath to break down the material.

The acid causes the bone samples to become soft, allowing researchers to extract a protein, collagen.

(intense music) Once concentrated, these collagen molecules are placed in small tin capsules to be analyzed by a mass spectrometer.

A few months later, they receive the first results.

- [Interpreter] So this is a map showing the probabilities for oxygen's.

- [Interpreter] Ah, it's much more pronounced.

- [Interpreter] Once again Paris, here.

And in terms of probability, we can see that the higher values are further east in France.

- [Narrator] The analysis says the mystery man grew up in the east of France.

This result matches with the little information the archeologists gathered so far about Edouard de la Madeleine, who belonged to a noble family based in Burgundy.

(intense music)