Alex found the tracks of his uncle's path in the mines under Sayle Enterprises. When he was inside the mines, he found out that Stormbreaker was just not a school computer, but was a device that was going to kill millions of people in one day.
When Sayle found out that Alex was not really Felix but was working for M16, he tried to kill him by putting him in a tank with the worlds deadliest jelly fish. When Alex broke out, he killed Sayles's assistant with the jelly fish and then proceeded to stop Sayle from releasing the Stormbreaker.
When Sayle tried to leave by plane, Alex stole a jeep and was chasing him down the runway. He was being shot at by guards. When he reached the plane, he jumped out of the truck and got into the cargo of the plane secretly following Herrod Sayle.
Once they landed in the museum for the ceremony for the Stormbreaker, Alex ran off and hid. When the time came to put the Stormbreakers online, Alex shot Herrod Sayle saving millions of people from the disease from the computer.