Sherlock Holmes Chapter One

The best way to obtain this is to play through and focus on the game's main story quests all the way up until the end of Sacrificial Lamb. You'll get your final clue and unlock the door to the garden back at your mansion. That door is the end of the game and the point of no return - don't go through it until you've gotten the rest of the achievements!

Don't worry, Jon will be leaning against the door, and he'll warn you before you go through, so you can't just accidentally click it. It's the door directly opposite the front door, in the little hallway behind the stairs.

This is where you should pause and do all of your side content - you have to complete all of the cases and stories around town, bandit lairs, etc.

I say to go that far because in order to get all the furniture unlocks for The Tale of the Empty House, you have to progress the main story for the merchants to be stocked. Technically, as soon as you *start* the Sacrificial Lamb quest, you can buy everything.

The only two achievements you should have left to unlock before going into the garden are Closing a Chapter and this one. As soon as you make your final decision, Closing a Chapter will pop, and then this right after.