In 1887, Robert Ledru was regarded as one of France’s most talented detectives.

The 35-year-old investigator worked in Paris, but his reputation stretched far beyond the French capital. Whenever police departments elsewhere in the country encountered particularly difficult cases, Ledru would sometimes be called in to help.

That year, one such investigation took him to a coastal town in northern France.

A string of sailors had mysteriously disappeared from the area. Nobody seemed to know where they had gone or what had happened to them.

Local police were struggling for answers.

So they called Robert Ledru.

But shortly after his arrival, the celebrated detective would become involved in a completely different investigation — one that would lead him to perhaps the most disturbing discovery of his career.

He would solve a murder.

And, according to the evidence, the killer was himself.

A Mysterious Murder on the Beach

Ledru arrived in the coastal town late at night.

Tired from his journey, he went directly to his hotel and climbed into bed. The following morning, he got up and headed to the local police department, expecting to meet the officers who would help him investigate the missing sailors.

But when he arrived, the situation had changed.

During the night, a murder had been committed on the beach.

The missing sailors investigation had been lowered in priority. The killing was now the police department’s main focus.

The local officers apologised to Ledru. They explained that he had travelled all that way to investigate the disappearances, only for their attention to suddenly shift elsewhere.

Since he was already there, however, they asked whether he would help with the beach murder.

Ledru agreed.

The victim was a middle-aged man named Andre Monae.

Monae had owned a dress shop in Paris before recently moving to the coastal town. He had apparently come to the area to enjoy its beautiful scenery.

Early that morning, his body had been discovered on the beach.

Investigators quickly determined that Monae had been killed by a single gunshot to the chest. The bullet had passed completely through his body and exited from the other side.

But the bullet itself was missing.

Police had no suspects.

They had no meaningful leads.

And there was no obvious motive.

Robbery appeared unlikely because money was still found inside Monae’s pockets.

With little information to work with, Ledru joined the local officers and travelled to the beach.

Barely Visible Footprints in the Sand

At the crime scene, local police concentrated on finding the missing bullet.

Ledru took a different approach.

He began walking a short distance along the beach, looking for anything investigators might have overlooked during their initial search.

He did not have to walk far.

Ledru noticed a series of barely visible footprints in the sand.

The prints appeared to pass directly by the location where Andre Monae’s body had been found. They continued beyond the crime scene before leading towards a flight of stairs.

The footprints went up the stairs to the road.

Then they disappeared.

Ledru immediately called the other officers over.

He instructed them to make plaster casts of the footprints so that he could study them more closely.

The process involved pouring liquid plaster directly into the impressions in the sand. Once the plaster dried, investigators could remove it, creating a three-dimensional model of the foot that had left the print.

As the officers worked, Ledru stared at the footprints.

Something was bothering him.

He told one of the officers that the prints looked strange.

More importantly, they seemed familiar.

Ledru felt as though he had seen footprints like them before, but he could not remember where.

Less than an hour later, the plaster had dried.

The officers removed the casts and handed them to Ledru.

The detective looked at them.

His reaction was immediate.

Ledru appeared physically disturbed by what he was seeing. His expression reportedly suggested disappointment.

But he said nothing.

Instead, carrying the plaster casts, he walked away from the officers and continued down the beach.

The Detective Sat Alone for Hours

Ledru eventually reached a secluded section of the beach.

He sat down.

Then he simply stared at the plaster casts.

Hours passed.

The sun blazed down on him, but Ledru appeared unaffected. The tide slowly began creeping towards his position.

Still, he remained seated.

The local police officers watched from a distance.

They knew little about Ledru personally. What they did know was his extraordinary reputation.

To them, he was a legendary detective.

For that reason, they were reluctant to question his unusual behaviour. Perhaps this was simply part of his investigative method.

By mid-afternoon, Ledru finally put down the plaster casts.

He stood and walked back towards the mystified officers.

When he reached them, he made an astonishing statement.

“There is no reason to stay at the beach any longer or interview any more witnesses. I think I’ve solved the case.”

Ledru did not explain himself.

Instead, he turned around, left the beach and headed back to his hotel.

The local officers looked at one another.

Confused, they eventually left as well.

The Missing Bullet Is Found

Early the following day, investigators finally discovered the bullet that had killed Andre Monae.

When Ledru returned to the beach, the local chief of police handed him the bullet, hoping it would help move the investigation forward.

Ledru examined it.

Then he sighed.

“Okay, now I know for sure what happened,” he said.

The detective proceeded to reconstruct the murder.

According to Ledru, the killer had woken in the middle of the night on the night Monae died.

He got out of bed.

He put on his clothes.

Then he walked down to the beach.

There, the killer encountered Andre Monae, a man he did not know. Ledru believed Monae had probably been taking a midnight stroll.

The two strangers began having a friendly conversation.

But at some point, something changed.

The conversation turned into a quarrel.

The killer drew his pistol.

He shot Andre Monae in the chest.

Then he fled.

The police chief listened as Ledru described the crime in extraordinary detail.

There was an obvious question.

How could he possibly know exactly what the killer had done?

Ledru gave him the answer.

He was the killer.

Robert Ledru Had Caught Himself

Ledru told the police chief that he had killed Andre Monae.

But he insisted he had not done it deliberately.

In fact, he had no memory of committing the murder.

Ledru believed he had killed Monae while sleepwalking.

The plaster casts had first made him suspicious.

When Ledru examined the casts, he finally understood why the footprints had seemed so familiar.

The person who made them was missing a toe.

Robert Ledru was also missing a toe.

The footprints looked exactly like his own.

There was another disturbing piece of evidence.

That morning, before Ledru had even travelled to the beach, he had noticed something strange inside his hotel room.

His shoes and socks were beside his bed.

They were sandy.

And they were damp.

Ledru could not remember how they had become wet or covered in sand. At the time, he had considered it strange, but he was too busy preparing for the investigation to examine the matter further.

After spending hours staring at the plaster casts on the beach, however, the detective returned to his hotel room.

The first thing he did was retrieve his revolver from underneath his pillow.

Ledru always kept the weapon fully loaded.

One bullet was missing.

The Final Piece of Evidence

Ledru spent the rest of that night desperately trying to convince himself that everything was a coincidence.

Perhaps the footprints only resembled his own.

Perhaps there was another explanation for his sandy, damp shoes and socks.

Perhaps there was a reason one bullet was missing from his revolver.

Then, the following morning, police handed him the bullet recovered from the beach.

Ledru recognised the ammunition.

It was the same type of bullet he used in his revolver.

For the detective, there could no longer be any doubt.

He had killed Andre Monae.

Robert Ledru, one of France’s most talented investigators, had effectively caught himself.

Police Refused to Believe Their Star Detective Was a Killer

The local police were stunned.

At first, they refused to believe Ledru’s confession.

More specifically, they did not want to believe that the legendary detective they admired was responsible for a brutal homicide.

But investigators carefully examined the evidence.

The unusual footprints matched Ledru’s missing toe.

His shoes and socks had been sandy and damp.

A bullet was missing from his revolver.

And the bullet that killed Monae was the same type of ammunition Ledru used.

Eventually, police accepted the disturbing conclusion.

Robert Ledru had to be the killer.

However, one major question remained.

Had Ledru really committed the murder while sleepwalking?

Or was his claim an elaborate attempt to avoid responsibility?

Police decided to conduct an extraordinary experiment.

The Jail Cell Experiment

Ledru fully cooperated with the investigation.

He agreed to sleep inside a jail cell, where armed guards could monitor him 24 hours a day.

Inside the cell, police placed a revolver loaded with blank rounds.

Ledru was instructed to keep the weapon underneath his pillow, just as he had done at his hotel.

For the first several days, nothing happened.

During the day, Ledru never touched the revolver.

At night, while sleeping, he left the weapon alone.

Then, about a week into the experiment, everything changed.

In the middle of the night, Ledru suddenly woke.

But he appeared to be in a trance-like state.

He reached underneath his pillow.

He grabbed the revolver.

Then he began firing at the armed guards standing outside his jail cell.

The revolver contained blanks, so the guards were not shot.

But the experiment had produced terrifying evidence.

Police became convinced that Ledru had been telling the truth.

He really had killed Andre Monae while sleepwalking.

A Detective Exiled for the Rest of His Life

Authorities ultimately decided not to prosecute Robert Ledru for Andre Monae’s murder.

Instead, they chose a highly unusual solution.

For the protection of everyone around him, Ledru was effectively exiled.

He was forced to live alone on a secluded farm outside Paris.

There, he remained isolated from society.

The only people who visited him were doctors.

Even they would only arrive during daylight hours.

And they came accompanied by armed bodyguards.

Robert Ledru remained on the secluded farm until 1937, when he died.

His extraordinary case has endured as the disturbing story of a brilliant detective who followed the evidence of a seemingly impossible murder — only to discover that every clue pointed back to himself.

He had solved the case.

But in doing so, Robert Ledru had caught the one suspect he could never have expected: himself.