Bert's nightvision isn't nearly so good, but he trusts what Karkat sees and that Karkat can also see the smile that he gets when he hears who they're heading toward.

"This gift is too good to pass up. And the least we can do is make it a good show for the people back home. I say we jump him and slit his throat."

After what happened last time Cuthbert wasn't in the mood for tricks or traps or anything fancy. Just a humiliating death for the man he had dreamed of getting a second chance at.