All The Party knew of Ferrin himself is that he was a human male whom Leithe contracted to buy burger buns from, whose house seemed innocent enough in Goldvale. Ultimately they met a random transient NPC human named Darius who was hunting The Cult Of Alden and had info that Ferrin's house was a place to investigate.
(Battle At Ferrin's House)
When PCs arrived at Ferrin's House they found the front door ajar, the Darius NPC dead inside, and a cult member locked in combat with a soldier. The house was a facade for a two level dungeon1), and didn't help clear up who the supposed local Ferrin was. Above the front door was the triangle symbol known to be associated with The Cult Of Alden. After tense standoff, wherein the cultist argued that the soldier and his buddies were there to unleash things from below upon the world for their own benefit, which is arguably evil. In turn the soldier argued that the cultists were evil and this stronghold needed to be destroyed. The party sided with the soldier, murdered the cultist, and then not long after upon finding a stairway down to a second level, the soldier was killed by hostiles below before the party could progress.
Below2) in various rooms were soldiers aligned with wizards. Cultists aligned with a goblin. Everyone was holding strategic positions and taking pot shots at anyone who dared wander the hallways. PCs quickly figured this was dangerous and skirted the main combat to find several more doors, all with various beings behind them. A little paranoid experimentation of listening to doors, and having earlier found a key that fit the doors, led to the release of some creatures that were probably being held by The Cult Of Alden for blood sacrifices, although they had no way to know that was the purpose at the time.
Since the party took off rapidly they didn't know what became of the battle inside the dungeon there, but later in the day it was noted that smoke was rising from that area. Thus went the battle at Ferrin's House, which would them become thought of as “Ferrin's Ruin”. Socks & Sunny were adopted by Jules & Eyrun.