An unseen crook would have to maintain a secret headquarters.

It's the secret headquarters of the world's most evil villain.

"Hey, how did you find the secret headquarters, anyway?"

"You are seeing the secret headquarters of the mutineers," he said.

Once there, Reynolds is kidnapped by freedom fighters who take him to the professor's secret headquarters.

In the secret headquarters on the mountain they receive training.

Another secret headquarters up in smoke, she grieved, shaking her head.

When she refuses to act against 326, he confines her to a room in his secret headquarters.

"We might break and spill the whereabouts of the secret headquarters, or something."