The razor was an attempt to create mutually exclusive versions of what happened.
Ok, they presented the razor as if it were a Chekhov's Gun
, but it was never shown or referenced again. Furthermore, the movie was clearly set-up to suggest that some or all of the events might have occurred in Lawerence's mind (a particularly cynical interpretation might say he never left the asylum at all, and spent most of his childhood and his entire adult life there, after his father sent him there). And the scene in which his father comes to the asylum seems particularly suspect, as he just pops up after Lawrence has been tortured and tells Lawrence exactly what he wants to believe (I'm a monster, you're not crazy, and I love you even if only one some sick level). However, the razor allows us to accept the possibility of an escape that did not involve him being a werewolf: he hid it and was able to cut his bonds and escape out the window, possibly slashing some people with the razor. This is interesting, however, in that to accept that the realistic explanation (the razor let him escape) was real one must also accept that John Talbot came to the asylum, and told his son that his delusions were real, possibly trying to drive him to suicide, and if one accepts that the werewolf part was real, it makes the idea of John Talbot never actually confessing quite credible. In short: Whatever part of it is real is the part that Lawrence is unaware of.
Who is this kindly old man Lawrence meets on the train ride home? He's yet another Talbot. The family already seems to have a strong wolf motif (note the large statue of one seen as Lawrence is arriving at Talbot Hall) and why else might a perfect stranger give Larry a wolf’s-head cane he just so happens to have? Perhaps he is a brother to Sir John and thus an estranged uncle of Larry’s, away for most, if not all of his life. Hearing somehow about his younger nephew Ben Talbot's death and knowing of what Sir John is, he intended to return to Blackmoor and confront him personally, but upon meeting Lawrence, he decided to leave it to the son to bring down the father.
(This theory naturally ignores the novelization’s claim that Max von Sydow
’s character was a Frenchman. Or else, he may have just picked up the accent after spending a significant time there.)