After an incredibly decent meal at Jacob's, Peter was walking the pair towards the gates of die Festung. They wanted to see more, and though he'd explained again about the dangers outside the gates, Jesse in particular had been fairly adamant about going outside.
Since they were newcomers (to this world, at least) Peter couldn't leave them by themselves. So he was going to escort them and try his best to protect them from whatever might be out there this time.
Murphy might have a magic-or-not sword, but Peter had one as well, and two swords (plus a battery of other abilities ending with -kinesis) were better than one.
"Who knows?" he said. "Maybe it'll be fun. But you're not going out there without me."