The Dangerous Dilemma of Daphne Dixon, PI

Your friend, and local private investigator, Daphne Dixon ('Dix' for short), has gone missing. Earlier today, you received an envelope in the mail containing what looks like a mailbox key and a note simply signed 'D'. Worried, you head to her office building where you are pulled into her world of mystery and intrigue. Use your powers of deduction to solve the crime and help bring Dix to safety.