You need to Beat the 1st Puzzle as the Explorer.
Go and pick up the walkie-talkie on the table, then look for the bloody writing on the wall.
Across from this writing there is a wall with 2 lit up coloured eyes, and below them a bunch of symbols.
Tell your partner the eye colours that you have, and they need to describe the symbols that they have in their library. Once both are pressed successfully, the trophy will pop!