"Hmm, and how do you know none of us"--he gestures to himself and the other recent arrivals--"were here when the crime happened?" Ennius prods, "we weren't, of course, and can all vouch for each others' location--we only just boarded--but how are you certain of that?"

"Oh, furthermore, we saw nobody pass us as we came from the back of the train to here so unless someone could have hidden from us or made it inside that prison car, your culprit is either here or between here and the engine."