The hunt is over! Thanks so much for solving! Solutions are available for all puzzles. A wrap-up post will be coming in around a week late January.

3 Cats in a Trenchcoat

Solves

Total: 14

Toggle spoiler tags for secret content:
Puzzle Solve Time
17 Sack of Gifts
13 The Arcade
14 Ice Pack
6 September of the Puffins
11 Check It Out!
10 Flipping Channels
9 Overt Infiltration
8 Survival Stories
7 Spy Games
5 1. e4 e5
4 Subnivean Snake
3 Double-Crossed
2 Metrology Lab
1 Penguin Pidgin