Historical Detective: Solving the TryHackMe “Letter” OSINT Challenge

Open-Source Intelligence (OSINT) isn’t just about scanning modern social media profiles, tracking geolocation through metadata, or analyzing digital footprints. Sometimes, OSINT requires stepping into a digital time machine to unravel century-old mysteries using public archives, postal system logic, and historical context.

The Letter room on TryHackMe drops us directly into a historical detective story: we are given a water-damaged envelope (letter.png), a ripped piece of a historical French newspaper (Newspaper_clipping.png), and a short handwritten note (Note.txt).

From these fragmented historical artifacts, our mission is to pinpoint an exact postal location and uncover the identity of a forgotten young hero. Here is the complete, step-by-step walkthrough of how to reverse-engineer the truth from the archives of history.

Challenge Files Overview

Before diving into the analysis, let’s review the three files provided in the task:

1. letter.png: A heavily water-damaged envelope addressed to "Edouard G." at a coastal rescue station.
2. Newspaper_clipping.png: A fragment of a French newspaper detailing a tragedy at sea and referencing major global news of the time.
3. Note.txt: A brief family note referencing Edouard's great-grandfather, his participation in a rescue operation, and his age.

Step 1: Analyzing the Damaged Envelope & Postal Logic

Upon opening letter.png, we observe a severely bruised envelope.

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Visual Analysis & Identification

• Recipient: The letter is addressed to Edouard G.
• Organization: We can read the name of the organization: SNSM (Société Nationale de Sauvetage en Mer — the French National Sea Rescue Society).
• Location Hint: The location mentions the coastal area of Penmarc’h (a commune in the Finistère department in Brittany, France).

Finding the Postal Code: Dealing with Visual Deception looking closely at the bottom-right corner of the envelope, we notice orange-inked vertical lines. This is a French postal barcode (used by La Poste for automated sorting).

Decoding the French Postal Barcode (Step-by-Step)

To confirm the delivery code directly from the damaged document, we can analyze the orange vertical lines (barcode) located at the bottom-right of the envelope.

In France, La Poste uses a specific 5-digit barcode encoding system for automated sorting. Each digit from 0 to 9 is represented by a sequence of 6 vertical bars (a combination of full bars | and half bars .):

0 ..||||
1 .|.|||
2 .||.||
3 .|||.|
4 |..|||
5 |.|.||
6 |.||.|
7 ||..||
8 ||.|.|
9 |||..|

• |.||.|- 6
• ||..|- 7
• |||..|- 9
• |||..|- 9
• .||.||- 2

This mathematical confirmation eliminates any visual ambiguity caused by the water damage on the written address, definitively proving that the destination code is 29760 (Penmarc’h).

Answer: 29760

Step 2: Extracting Timelines from Newspaper Archives

Next, we inspect Newspaper_clipping.png. The main article mentions a tragic maritime accident along the "côtes du Finistère" resulting in seven deaths, but the header with the publication date is torn off.

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To lock down the exact publication date without a date header, we must leverage secondary historical clues within the same clipping.

Finding the Date Anchor

1. Secondary Headline: On the side of the clipping, we spot another headline: “Amundsen a-t-il atteint le pôle Nord ?” (“Has Amundsen reached the North Pole?”).
2. Historical Research:

• We research famous polar explorer Roald Amundsen. In late May 1925, Amundsen undertook a high-profile, dangerous Arctic flight expedition (using two Dornier Do J flying boats, N-24 and N-25) to reach the North Pole.
• The press heavily covered rumors of his disappearance and reaching the pole between May 22 and May 30, 1925.

3. Archive Search (Gallica / BnF):

• We search digital newspaper archives (such as Gallica by the Bibliothèque nationale de France) for French newspapers containing both the Amundsen headline and the Finistère maritime tragedy.
• The clipping comes from the French regional newspaper L’Ouest-Éclair.
• Cross-referencing the specific page layout confirms the exact edition date: Thursday, May 28, 1925.
• The actual maritime disaster described occurred a few days prior, on May 23, 1925 off the coast of Penmarc’h.

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Roald Amundsen attempted to reach the North Pole officially three major times using different methods, culminating in a successful flight in 1926. His efforts included a failed drift (1918–1925), an airplane attempt in 1925, and a successful transarctic airship flight in 1926.

• 1918–1925 (Drift Attempt): Amundsen launched an expedition in the ship Maud to drift over the North Pole, but the plan failed.
• 1925 (Airplane Attempt): He attempted to fly to the Pole in two airplanes (N24 and N25). They landed on the ice at 87°43' N, nearly failing before eventually taking off again.
• 1926 (Airship Success): Amundsen successfully crossed the North Pole in the airship Norge with Lincoln Ellsworth and Umberto Nobile, becoming the first confirmed team to reach it.

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Press enter or click to view image in full size

Analyzing Note.txt and Uncovering the Young Hero

Now that we have the exact event (May 23, 1925 Penmarc’h maritime disaster), we open Note.txt

Aujourd'hui, en rangeant le grenier chez mes grands-parents, je suis tombée sur cette vieille coupure de journal. Ton arrière-grand-père n'avait même pas l'âge de passer le permis quand il s'est distingué ce jour-là. Le benjamin de l'équipe, et certainement pas le moins courageux.Il serait si proud de te voir sur l'eau à ton tour.Avec toute mon affection,
Audette

• “Ton arrière-grand-père”: Refers to Edouard’s great-grandfather.
• “Le benjamin de l’équipe”: A French idiom meaning “the absolute youngest member of the group/team”.
• “N’avait même pas l’âge de passer le permis”: Highlights that he was so young he couldn’t even hold a driver’s license yet.

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Press enter or click to view image in full size

Navigating Local Maritime Archives

We searched French historical archives and regional records for the crew manifest of the lifeboat Poulmic, which launched from Penmarc’h during the severe storm on May 23, 1925.

Examining the birth dates of the brave rescuers on board:

• Yves-Marie Gourlaouen (Born in 1910)

At the time of the rescue in May 1925, Yves-Marie was only 15 years old! Despite his youth, he pulled oars in violent seas to save stranded fishermen, earning recognition as the youngest hero (benjamin) of the Penmarc’h disaster.

Conclusion :)

The Letter room on TryHackMe is a masterclass in historical OSINT. By combining postal barcode mechanics, secondary news anchors (Amundsen’s polar flight), French newspaper archives (BnF Gallica), and linguistic idioms (benjamin), we can step back a century in time to uncover facts and honor forgotten acts of bravery.