Maybe those necklaces are made out of the eyes of people like the MC? So, the knight would want to secure the kid and report to the emperor so that the emperor can have the MC's eyes gouged out and turned into two more necklaces? However, the knight didn't actually want to seize her, let alone attack her, as he might not know the exact process, like if they first need the kid to grow up some more. He might ruin the eyes by acting haphazardly.