GRENOBLE, France—It started with the disappearance of 8-year-old Maëlys de Araujo at a wedding in the French Alps. After a massive search that drew nationwide attention, investigators identified a wedding guest as the main suspect. But that was just the beginning: The investigation led authorities to suspect the man in other crimes around France. Dog trainer Nordahl Lelandais goes on trial Monday in Grenoble accused of kidnapping and killing Maëlys. He faces up to life in prison if convicted. The search for Maëlys, and the gruesome discovery of her body six months later after Lelandais admitted to killing her, gripped France, and tore the girl’s family apart. The trial started on Monday morning in the presence of Maëlys’ parents. The girl’s mother kept a large picture of her daughter in her hands. Lelandais told the court he wanted to apologize. “I indeed took the life of Maëlys. I didn’t want …