A Trove of Secrets
SPOILERS AHEAD! BE WARNED!
The letter inside is typed, unsigned. Parts are encrypted, but others record the recent movements of a Careworn Journalist. His visits to bare-knuckle fights. His regular appointments with an Anxious Auditor at Beatrice's Tea Parlour.
Unlocked with a redirect from Making your name: steal a Revolutionary communication or You have stolen an important secret from a courier