From the WotC series plot recap:
Much that occurs in this land escapes the histories and records slumbering in dusty vaults and the dim halls of kings. And so it is with the working of Mielikki and her regents. Much of their story remains written only in the veins of leaves and the moving of winds and waters through the High Forest. Yet, I learned this tale elsewhere still: from the songs of a grig prince named Feythrin, who unwittingly stumbled upon a great adventure.
Now that villain the Hark entrenched himself between Loudwater and Secomber. For decades the wererat bandit lord harassed caravans and wayfarers traveling the roads and rivers. The fearless and cunning hit-and-run raids were legendary but thankfully sporadic among those traveling the corridor. Trading coster owners typically referred to losses suffered during these raids as the "Hark's Tax," and they were resigned to consider it a cost of business in the area. Other folk where not so resigned. This tax was not paid in goods only, many paid with their lives.
Lately the attacks were becoming more daring, more successful and frighteningly more common. Combined with the tension of orcs migrating eastward en masse from the High Forest, the Hark's renewed vigor bode ill for peace and stability in the region. Rumors of a young red hunting the northern faces of the Greypeak Mountains did nothing to quelling the mounting anxiety.
Worry was everywhere, but few paid as dearly in misery as Blaz Merrymar of Shining Falls. Stolen merchandise was inconsequential compared to the lives of four sons and three nephews lost. Added to his woes were thoughts of leaving a widowed wife to fend for his two remaining daughters, for Blaz was captured along the road by Skar and his bugbear pet, Gvrag—and they were agents of the Hark.
Groef Feythrin knew a great deal about these goblinoid raiders having played pranks on them a time or two, and their greedy voices scrapping through the evening air attracted his whimsy.
"This half-man has looser skin than the other. We must be getting to the bottom of the barrel," barked Skar. "The boss will be well pleased," replied another.
Much merrier my midnight mirth promises making them my momentary mischief, thought Feythrin, and off he sprung fiddle in hand. Shortly he came upon a gruesome scene. Blaz held aloft by Gvrag twisted and contorted away from a torch flame held by Skar. Sadly these sorry suckers mistook sickness as silliness so this sad sap suffers, lamented Feythrin. Yet, he was not the only witness to Blaz's distress. Nor was he alone in his desire to work mischief upon the bandits.
Coming along the road was a motley band of adventurers. Having met this very day and finding each other good company, they joined forces for the long road home. Some were out patrolling the road to secure the peace, some were returning from Fools Finger with their souvenirs' for Hedris Teinel and some sought new adventure after failing to locate the ancient dwarven complex of Iirikos Stonesholder. They just decided to make camp when they stumbled upon Blaz in his plight. Heroes all, they rushed in and made quick work of Skar and his minions.
It's clear the Blaz was saved, and for this Feythrin was glad, but what follows this heroic rescue remains for others to tell because the groef's song does not say. Cross at loosing his goblin entertainers, Feythrin departed to amuse himself elsewhere. Yet, the paths of the bold cross many times in the winding wood; the brave adventurers re-emerge in the little prince's song.
Whether motivated by Blaz's fierce hatred for those who murdered his kin, employed by Gauntlet Harazos Thelbrimm of Loudwater to "clear the road," or answering an inner voice marking all persons of great character, the adventurers returned to the wood tracking the goblins to their lair to cleanse the foul den. Earnest in their task, they failed to notice jostling Feythrin's bower were he lay dreaming about purple buttons.
Rudely woken, Feythrin resigned himself to keep these large folk in his debt until by song of deed they amused him greatly, Feythrin drew a determined breath and leapt off to follow his newly appointed deputies of delight.
Eventually, the tracks lead to a macabre camp. Two curious holes in the earth revealed the vile industry of the Hark's crew. The flesh and bones of birds, beasts and unfortunate travelers filled one hole. Crows now feasted on the scraps.
The second hole was actually a tunnel leading to the river and a raft. Putting all the pieces together, the adventurers pinpointed the location of the bandit's hideout and began their assault. Here, Feythrin's song becomes confusing for he claims the truth is disguised by tears of mirth which fiddling tells better then words. So he plays and his music evokes much splashing and clambering and climbing and scrambling and yelling. When he sings again the mirth is gone for there is a battle by water and under stone and into the very face of the cliffs.
Feythrin took to flight and reaching the cave entrance all was silent. The shattered frames of fallen foes lay about the hideout, but there was no sign of the heroes. He pressed deeper into the gloom and rounding a corner spotted the adventurers as a shrill whistle split the air.
Suddenly, everyone was rushing forward again, and the clash and clamber of metal and magic filled the air. Feythrin leap forward just in time to see a wererat disappear down a large hole followed by an avalanche of stone cutting off any chance of pursuit. The whistling obviously gave the wretched creature the extra few seconds needed for escape.
While the villain fled and the band missed a chance to strike a decisive blow against the Hark's operations, all was not lost. The wererat that escaped was named Hekkut. Whether by Tamora's hand or a streak of vanity, Hekkut left scribbled on the cave wall much of the Hark's present plans.
It took close scrutiny to decipher the script, but Hekkut's notes recounted many things such as his and the goblins' trek from the Hark's stronghold, through the illithid-infested corridors of the Underdark to these caves. Apparently, the Hark allied himself with mindflayers and something called the Forest King in a bid to expand his territory deeper into the Delimbiyr Crescent.
Having cleared the den and with new information important to securing the future of Loudwater, the adventurers returned home. Feythrin followed them secretly to the edge of his realm, bid them farewell and with leapt off to manage his realm.
Fools Finger: In the Greypeak Mountains, about a three day hike from Shining Falls, leans a great crumbling obelisk of unknown origin that locals call Fools Finger. The rock of this obelisk radiates with a cool emanation and a rosy red color. Hendris Teinel, the patron of the Scarlet Shield, has promised any adventurer bringing back a souvenir from this monument—a piece of the magical rock no smaller than his own big toe (which is rather large as far as big toes go)—wins free dinners nightly. Hendris craves the magic stone into shield shapes, and sells them to merchants heading to Waterdeep, where they are the rave of nobles and adventurers who use it to cool and illuminate their drinks. While the food is rather bland, a guaranteed meal ticket has motivated a lot of adventurers to take the trek. Many even return.