It's a secret underground facility located on an island off the coast of Scotland. It's actually a highly advanced weapons factory, where villainous millionaire, Mr. Grin, is producing powerful, highly dangerous weapons for his own nefarious purposes.
Here's a little more detail:
* Secret Location: The Ark is very well hidden, and it's accessed through a secret entrance.
* Advanced Technology: The facility boasts sophisticated equipment and a highly skilled workforce.
* Weapon Production: It's where Mr. Grin manufactures various weapons, including the titular Stormbreaker, a unique and deadly weapon.
* Hidden Agenda: Mr. Grin intends to use these weapons to control the world and make a massive profit.
Alex Rider, the teenage spy, infiltrates the Ark to expose Mr. Grin's activities and ultimately prevent his plans from coming to fruition.