Ariane's fish as Etain arrives?
So we see Ariane catching fish and hurling them onto the riverbank as Quintus pees in the river- then he sees that the hunting Picts with Etain are coming, and the two dash to the hut without the flapping fish.
So, as keen and observant as Etain is- or the others sat outside on horseback whilst she suspects and goes inside the hut (not to mention as they approach from that direction near enough) nobody sees the flailing fish nearby, a sign of human panic? Or why Ariane's clothes are wet?