I’m pretty sure now that the Derek-Chris lighter fluid scene will be a dream, most likely Chris’s nightmare, or Allison’s. Speculation has been that it’s a ruse to distract or draw out the Nogitsune, it’s what I thought too. But I’ve been trying to think of a context where such a ruse would be useful or practical, and I can’t think of one. It’d have to be done in front of Stiles to have an effect, and I’m not sure it’d have that much of an effect anyway. It made sense when I thought the Nogitsune might be hiding in Allison, but I don’t really believe that anymore. If it’s just Stiles, then what’s the point of such a display?
However, if it’s a nightmare sequence, that makes sense. Since there have been many nightmares this season, it would be very plausible as a nightmare of Allison’s. If the fox makes them all question their reality, that’d be a pretty terrifying thing.