Why did Alex go back into the train tunnel in point blanc?

In "Point Blanc," Alex Rider returns to the train tunnel to investigate the mysterious circumstances surrounding the deaths of several individuals and to uncover the truth behind the secretive school. His determination to protect his friends and prevent further danger drives him to confront the risks involved. Additionally, Alex's resourcefulness and courage compel him to delve deeper into the investigation, seeking answers that could thwart a larger threat.