Alex Rider go on a field trip and meet Scorpia.
His father is a member of Scorpia, so so he was told.
So what is Scorpia. An assassin organization.
So they wanted to turn Alex and let him work for Scorpia instead of MI6 by showing him the video on how his father was killed.
Of course, there is an evil plot.
The bad guys want to kill children in way to blackmail the country to cut tie with the American.