Warning This Section Does Contain Spoilers
Using the scanned journal page with the sketch of the horseman, we know that the archive we are to open this episode is the "Horseman" archive. Using Jasper's joke in his letter in conjunction with the grasshopper print we know that the password for the Horseman archive is "HANDS". To see how to solve this cypher please visit here.
Words to note for this archive:
At this point we cannot do anything more with the archives other than document the words and put a pin in it for later.