Riding the Rails of Density

S4 RISK SPOILERS! Felix is on the train to London, pretending to be his cousin Adrien, his mind spinning from his recent discoveries. Lila sits next to him, thrilled to be by Adrien's side... but she's beginning to sense that something's a bit off about him. When she begins questioning him, fishing out the truth, neither one expects what they'll hear next. (Crackfic. One-shot.)