Unsolved: Tracking Terror

Unsolved: Tracking Terror is a side quest in the Fallout 76 update Wild Appalachia.

Detailed walkthrough
The quest starts upon reading the note either on Calvin van Lowe's bulletin board in his room at Van Lowe Taxidermy or pinned to the bottom of the bulletin board at Lewisburg Station.

The next task involves investigating the Monongah police station, located at the northwestern end of Camden Avenue, to find three notes; the forensics report (on the left side of the front counter, under a box of Dandy Boy Apples), the animal control report (on a file cabinet on the second floor, between the armory and the bathroom) and the incident evaluation (in the bottom drawer of a file cabinet to the left of the terminal). The last clue is found by accessing the nearby terminal and reading the Incident Report 1542.

The previously picked up animal control report mentioned a lake, which happens to be the lake right next to Site Alpha. Once there, search and read the following notes; the page from Dr. Frank's journal (near a pile of bones on the southwestern side of the lake) and Jackson's notes (on a shelf near the elevator inside the shack). Note that both of notes cannot be picked up.

Follow the river westwards, trying to track the mysterious animal upstream by searching for signs, in this case several piles of bones near the stream as well as another non-collectable note, the last page from Dr. Frank's journal (on the eastern bank of the upstream lake, southeast of Big Fred's BBQ Shack). On the way here, one may encounter the son of Fluffy, a unique yao guai. However, since a random encounter takes place on the northern shore, chances are that the yao guai may be killed by it.

The final task is to search Fluffy's den for clues, with the den being located at the southwestern tip of the lake. Inspect both the skeleton of Dr. Frank on the ground and his journal next to him, as well as the "dead mutated bear", which turns out to be Subject J12: Fluffy.

Investigating everything in the den, including Fluffy, completes the quest and solves the final mystery that Calvin van Lowe went crazy over in thinking it would lead him to the fabled Sheepsquatch.