The note "What's in a name?" says something about ripping the red stitching in Grigor's satchel. Ha! Once Grigor leaves again (which he does once you finish with the flies) --
Hint 5
-- you can go to the bag and just rip open that stitching; no need to look for a knife.
Hint 6
This is ... odd information. You probably ought to ask first the Hardy boys and then Grigor about this.