The Detention Room shortly follows on from the Mutated Margurite boss fight, now you have found the Attic Lantern. After that, with the Crow Key you can gain access to a powerful weapon, as well as a trip back down to the Main House B1 for the Snake Key.
If you're after help for parts of the game, consult our complete Resident Evil 7 walkthrough and guide.
Where to find the Detention Room secret passage
With the Lantern in hand, return to the Old House 1F Attic, and at the end of the room by the door place the item on the scales, opening the way onward.
This entire floor has nothing to collect, so soak up the spooky atmosphere and investigate the notes as you travel from the Kid's Room, the Diseased Room and then the Detention Room.
In the Detention Room, check the doll's house in the corner to find a clue showing a secret behind the bed.
If you crouch behind the bed and look at the wall, you'll see an outline. Push against it and you'll find a secret area, with the D-Series Arm inside.
Now make your way back out of the house. You'll encounter a few Molded on the way - feel free to fight them, or simply run past them - and as you attempt to leave the Altar, the phone will ring. Take the call, then head back to the Trailer.
After the call, look in the fridge and rotate the object and read the note to add the 'Memo on Deputy's Head' to your file, informing you need to go to the Dissection Room.
How to get the Grenade Launcher in Resident Evil 7
But before you go to the Dissection Room, let's use the other room yet to be opened by our Crow Key. Head back into the Main House, then into the eastern wing, and south to the Drawing Room, where you can now unlock the door into Supplies. Here is where the Grenade Launcher and various consumables await.
Thankfully there is zero resistance on the way there or back, and once you're done, you can deposit your Crow Key in the Item Box and be done with it.
Want more help? Our Resident Evil 7 walkthrough and guide provides step-by-step instructions on how to survive the main story, as well as finding the Shotgun, Grenade Launcher and the game's many Lockpicks and Treasure Photos. Meanwhile, our Antique Coins locations, Mr Everywhere statue locations and File locations lists will help you find every available collectible on Normal and Easy difficulties. We also explain how to get the Dirty Coin item in the game by getting the best Resident Evil 7 demo ending, and for DLC, the full Bedroom solution, getting the Daughters True Ending, how to beat Hoffman at Blackjack in 21 and finishing Nightmare mode.
How to get the Snake Key in Resident Evil 7
Head into the B1 Processing Area (in case you forgot, it's via the north east Main House safe house). Go via the Boiler Room as usual, and watch out for the surprise monster that bursts through the wall when you go down the steps to the Morgue area. These are quicker than standard Molded, but the same rules apply; back away and aim for the head.
Head up to the Dissection Room, and investigate the corpse from the neck, giving you the Snake Key.
Exit the room, and two enemies will be on the stairs to the left. Your best move is to ignore them, turn right and sprint down the steps, and open the Snake Key at the bottom.
Make your way back up to the safe room in the Main House 1F, sprinting past any enemies as you go to safety. With the Snake Key in hand, you can access two upstairs areas - the Kid's Room, and the Master Bedroom. You can visit these in either order, but we opted for the Kid's Room first.