Unknown

I found a strange note on a TerraGroup form. It talks about the will of the Unknowns and the fuel needed for "purification." TerraGroup is somehow involved, and I should look into these Unknowns.
First, I should find out more about the fuel. It looks like the work of TerraGroup Labs.
- Find out more about TerraGroup's activities
- Achievement "Unknown"
To initiate the storyline, you need to find a letter at the TerraGroup security post in the Streets of Tarkov location, near the Cardinal residential complex.
After this, the trail will lead to the Laboratory location, where you'll need to find additional information and documentation.
One document is stored on a cabinet in the office marked O21, near the research wing of the location.
The second folder with documentation is stored in a medical container in sector O11, near the orange dome (between the research apparatus and the monitor). After finding it, you must leave the location.
Next, head to the Factory location near the medical tend. You'll find another document on yellow barrels next to the blue tanks. Leave the location.
Afterward, head to the Streets of Tarkov location near the Lexos store. Nearby, along Primorsky Prospekt, there's a wrecked gray G-Wagen. Loot Rzhevsky's character's property—a hard drive—between the seats. We leave the location and craft the disk decryption in the Intelligence Center.
The tip from the hard drive leads us to the basements of the Factory location, to a room with a hermetic door near the exit from the Scav location "Bunker Door." To open the room, you'll need the TerraGroup warehouse keycard. Take the documentation from the safe and on the shelf.
We return to the lecture hall of the Laboratory location, marked R16, where two audio cassettes can be found on tables with laptops and on the floor.
The recordings give us a new subtask: proceed to the Shore location in the eastern wing of the sanatorium. On the first floor, at the reception desk of the east wing, we find a note mentioning room 305, where a TerraGroup employee stayed.
In room 305 of the east wing, we take the note near the telephone, the flash drive in the laptop, and the key to the service apartment. We leave the location to decrypt the data in the safehouse's intelligence center.
After decrypting, we speak with the Mechanic, who takes over the decryption task. Mr. Kerman then contacts us, questioning the Mechanic's results and offering assistance. Additional crafting materials appear in the intelligence center along with laboratory cards.
We select the crafting material with the green keycard, as it's the only correct solution, and with the key to the TerraGroup corporate apartment, we proceed to the Cardinal residential complex on Tarkov Street.
On the first floor, we use the corporate key and open the next room with the crafted keycard. Carefully search the room containing four documents. Finding them completes the storyline.
The "Breadcrumb Trail" achievement is unlocked.