Asterion had noticed Antigone had disappeared while he was not paying attention, though when she didn't return he started to worry. He had someone check the toilets, and when she wasn't in there he stepped through the public area and outside. That was when he heard the yelling in the alley.
He darted around the corner in time to hear Antigone yell that the man was going to have to kill her to get her to stop, and that was when he recognised the man as Ares.
"NO!" Asterion yelled, rushing forward. He put himself between Ares and Antigone, glaring at Ares. "Leave her alone," he growled, his voice low.