[Fish Sandwich]

Since you specifically asked to be corrected, I will point out that episode 23 draws specific attention to the incense burner thing Garima has on the train, with the strong implication it's the scent that was used to mark the victims and track them down later. I don't recall if that ever gets mentioned in dialogue explicitly, but the information is definitely there in the visuals. Although, considering it's meant to be a mystery throughout 24, I suppose it's exactly what the show intended if the significance of it all went over your head in the immediate moment.