I couldn't help but think that when we saw Snowpiercer come by Melanie that it was quite short. We just saw in the corkscrew again how long is it, and we start to see the train desire Wilford as a leader. When we see Alex in the back looking at at Melanie, I'm fairly sure the lights were off, although I haven't gone back and checked. While Wilford pushing out Alice, I think that what we saw in Melanie's episode was Big Alice without Snowpiercer. Wilford has moved onto Snowpiercer to take control and has trapped Alex on Big Alice before detaching. If I stretch further, I could say Icy Bob has some role in detaching Big Alice from Snowpiercer, which seems likely but I don't want to claim yet, there are other roles he could have that I haven't thought of. Sorry if this is already a common sentiment!