Milan's elite antiterrorism DIGOS police receive a tip that a sleeper cell of Muslim terrorists have received toxic chemicals from Pakistan to make deadly sarin gas. The cell leader, a highly educated Italian-Pakistani engineer, has access to Milan's centers of finance, technology, commerce, and entertainment — all high profile targets with hundreds of casualties in a terrorist attack.

But the police have no names or leads to identify the terrorists. After months of investigation to infiltrate the cell, the police are stymied until they learn that the terrorists are using stolen cell phones to communicate.

Hours before the December 7 premiere of a new opera, DIGOS discover that the terrorists are targeting La Scala where hundreds of high profile political, diplomatic, and corporate executives are in the theater.