Warning: Contains Spoilers for His Dark Materials season 3, episode 2, "The Break," and Philip Pullman's book The Amber Spyglass.Will Parry's subtle knife breaks in His Dark Materials season 3, episode 2, but it can (and should) be fixed. The subtle knife was introduced in His Dark Materials season 2, where Will became its new bearer (at the cost of a couple of fingers). The double-edged blade is incredibly powerful - one side is able to cut through any material; the other can open windows to other worlds - which makes the knife breaking in His Dark Materials season 3, episode 2 all the more shocking.

Although Will has become increasingly adept at using the subtle knife, he has not yet perfected opening windows into other worlds. That's something Mrs. Coulter preys upon in His Dark Materials season 3. While Will is attempting to cut open a window, she distracts him with talk of his own mother.