A signal. It wasn't a bad idea, but as Luka tries to think of one, he finds its proving more difficult than it should be. If Garrot won't be able to hear his conversation with the Protector, then the signal couldn't be verbal. But a purely visual signal would require Garrot to looking at the right time, and Luka couldn't guarantee that.

"It would need to be something you could notice immediately. If you can't hear us, it can't just be a phrase." Luka strokes his chin in thought. "But not something so bizarre as to put him on guard. I could pretend to take a phone call. I could call you?"