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To solve the Laboratory lever puzzle in Blue Prince, power the Laboratory, then pull lever 9 followed by lever 3. This unlocks Blackbridge Grotto permanently.
How to decode the Laboratory clue
The Laboratory contains an incomplete periodic table marked with numbers and a complete periodic table elsewhere in the room. Match the numbered positions to the chemical symbols on the complete table, then read the symbols in numerical order. The resulting string, PuSHThReEuPaFTeRnINe, reads: “Push three up after nine.”
A second clue appears in Randolph’s third letter in the Mail Room: 9↑3↑. It corroborates the order, but is not required to solve the puzzle.
Power the machine and pull the levers
- Connect the Laboratory’s ceiling ducts to a steam source, such as the Boiler Room, or to another powered duct room.
- Check that the machine’s power light is illuminated and its meter appears. If the light is off, the machine will not respond to the levers.
- Pull lever 9, then pull lever 3. Leave both levers in their default state.
If you deliberately divert power during the sequence, a community reference describes this workaround: pull lever 9, depower the Laboratory, operate other levers as needed, restore power, then pull lever 3.
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What the puzzle unlocks
The first successful activation triggers a cutscene and permanently unlocks Blackbridge Grotto through a door on the exterior Grounds. The Grotto provides access to connect to one offline terminal each day.
The Laboratory machine can be activated at most once per day. After the permanent Grotto unlock, the machine has no known further function, although you can enter the sequence again on later days.
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