[Japo]

Once they're "in hiding" there's no way you're catching them, that's why you must hurry. An agent goes in hiding once either he's accomplished his mission or he isn't able to any longer because you've foiled the crime. Everything depends on each agent's role in the crime, "Organizer", "Initiated plan" or "Contacted parties" are the first to hide and you should get them as soon as possible. Afterwards don't arrest anybody necessary for the crime until you've got the others located, then arrest everybody fast. If you need more time to find them steal some item (money, weapon, etc.) necessary for the crime but just steal, don't arrest the guy who has it if he's still necessary. Stealing that will delay the crime while the terrorists get another item. Once an agent necessary for the crime is arrested the rest will soon go into hiding.

You don't become a double agent, you get terrorist to act as so. Sometimes you find "incriminating evidence" when breaking into a building (always in the big red safes), and when you arrest the guy he accepts to serve as a double agent for you. You get twice as many points compared to just arresting him (that's how you can get scores over 1000 ?/oo), his comrades aren't alerted because he appears to continue working with them, and he informs you of his moves and meetings.