>>713851179
If the plan was taking them both, why does The Knight just immediately fuck off with Undyne as soon as she shows up? The Fuck Squad wasn't in any condition to actually stop her from taking Toriel.
Why did The Knight wait at all? That little plastic ball wasn't actually keeping Toriel safe or hidden. What was stopping The Knight from taking Toriel immediately?
What was the point of the whole plan to have Tenna keep The Fun Gang busy? Kris and The Knight were waiting for Undyne to show up, right? If the plan at that point was for The Knight to take both of them, why do they immediately just grab Undyne and fly to the exit after making a big show about taking Toriel with their Gaster hands?
Kris is working with The Knight, and they're both working for Carol. Carol wants the other people who know the codes to the Shelter gone so nobody (the SOUL) can interfere with what's happening down there.
Kris obviously doesn't want to put their mom in danger, and The Knight, who is/was December Holiday, clearly has some special connection to Kris and has sympathy for them, so they're willing to offer up Undyne as a hopefully acceptable substitute to Carol to keep Toriel out of harm's way. Kris is a good kid and doesn't really want anyone to be put in danger unnecessarily, so even then they tried to warn Undyne ahead of time, but ultimately they're willing to bend the knee and accept that there's nothing they can do but go along with the plan.