The best place to hide is in plain sight…

Though yeah, if the finale does turn into a Chrysalis attack, then this will probably go a few ways.

Either Thorax was tricking them all along, but Spike showing him the "magic of friendship" makes him betray his people at the last minute. In a moment of weakness, he helps Chrysalis enter the city and has to spend the rest of the finale trying to make up for it. Or when Chrysalis attacks, everyone immediately blames him for it, and he runs off back to Chrysalis but ends up saving the day at the last minute.

Hail Hydra