Dr. Joël Le Scouarnec was a veteran surgeon when the police burst into his home in 2017 searching for evidence after a girl who lived next door accused him of exposing himself to her.

What they discovered in his home, in a small town in western France, went well beyond anything to do with the girl’s case. Rooms were cluttered with boxes packed with sex toys and more than 20 dolls. One doll, the height of a 3-foot-3 child, was dressed in a white nightgown and laid out on a couch.

They also found computers and more than two dozen hard drives — some stuffed under his mattress — filled with child sexual abuse imagery.

Dr. Le Scouarnec, now 74, was eventually convicted of raping the child for penetrating her body with his finger, which reflects the definition of rape in France, and for raping and sexually assaulting three other women when they were girls, including two of his nieces. He was sentenced to 15 years in prison.

But that was only the beginning of the story. Months into the investigation, a police officer methodically going through the hard drives discovered hundreds of pages of the doctor’s personal diaries as well as two spreadsheets. His diaries elaborately detailed the sexual abuse of individual children and the spreadsheets listed many of their names, ages, addresses and synopses of the abuse they suffered, according to the investigative judge’s summary of the case.

Starting on Monday, based on that discovery, Dr. Le Scouarnec will be tried on charges of raping and sexually assaulting 299 people over 25 years — almost all his patients, almost all children at the time of the suspected abuse. The rape charges are mostly related to penetration with fingers. He has denied some charges of rape, but admitted to touching some patients’ genitals during medical examinations, while some were under anesthesia, according to an overview of the case by the investigating judge.