"Feodor Sverdlov," "Convince Me 2" and "Brendan Stryker" all in the same thread reminds me that Glebb was the only sleuth who was able to crack the identity of the creepy poster with the multiple screen names.
In mystery plots, villains always reveal themselves, and this one couldn't resist sending Glebby packages, supposedly from different posters but in the same handwriting from the same address.