Student or Learner
This is an excerpt from a novel, "The Invisible Man", by G.K.Chesterton:
"It's the writing of that fellow Welkin," said Smythe gruffly. "I haven't seen him for years, but he's always bothering me. Five times in the last fortnight he's had threatening letters left at my flat, and I can't even find out who leaves them, let alone if it is Welkin himself. The porter of the flats swears that no suspicious characters have been seen, and here he has pasted up a sort of dado on a public shop window, while the people in the shopó"
Smithe is saying this to another man after they saw a threatening sentence on the shop's window.
What does "let alone if it is Welkin himself" mean?
Thank you in advance.
and I can't even find out who leaves them, let alone if it is Welkin himself. = and I can't even find out who leaves them, or even if it is Welkin himself.