It should have been obvious, in retrospect. 

In fact, it had been obvious. He'd said so himself. "We should expect this Alfirin to be a Galtan woman, probably a noble, about 30 years old, and with access to our party. So, Catherine, except it couldn't possibly be Catherine, because – " 

Because what? He's known her since they were both sixteen? She's his friend? She was just becoming his friend again? Because the one thing he doesn't think he can bear is watching his friends start lying and plotting against each other in secret and waiting for the knife that might come from anywhere, not again, again and again and again and again – 

He feels like he should be standing on some bridge in Isarn, staring into the Sellen and lightly considering jumping in. So, in an instant, he is.