Hardened Detective difficulty:
Successfully complete the game under the Private Investigator
difficulty setting.

Mythos Master difficulty:
Successfully complete the game under the Hardened Detective
difficulty setting.

"A" rank:
Get a 100% game completion to earn an "A" rank. This can be done
by collecting all journal entries (thirteen in Jack''s Diary, eighteen
in General Evidence, and six in Mythos Tomes), finding the rifle a
reception office door in the refinery, saving Ruth from the rafters,
and keeping enough sailors alive during the boat ambush all under
three and a half hours with less than thirty saves done manually.

Variety Store: Safe combination:
The combination to the safe in the Variety Store is 2-6-1-2.