Jorin considers this for a moment and says, "I could challenge these rate people to a four-on-one wrestling match.  They are small things, and I am very strong."

Drusk uses Locate Creature.
Kelso has entered the South entrance of Trollskull Alley (200' SW of your current breakfast table). He moves 60' north (following the street contours), then 150' west, then 50' north. After a brief pause, Kelso moves another 20' north, then small movements around that spot.

After someone gets a map of the alley, you guess that Kelso has entered a building on the west side of Trollskull Alley.
That building is east of the Book Wyrm's Treasure, a bookstore/library that Hildigrim has visited occasionally. (Hildigrim does not remember what buildings were on either side of the bookstore, just the bookstore itself.)

As an aside, since Hildigrim has acquired arcane knowledge since his last visit, he may be interested in a service at that bookstore. Rishaal (a short gold Dragonborn) has a small collection of spellbooks and allows wizards to copy spells from them for a price. The cost table is in the spoiler:

Hildigrim begins down a rabbit hole centered on a series of books he wanted from Book Wyrm's Treasure, then jumps on a tangent of vocalized thoughts concerning the possibility of finding new books on the subject of his new arcane abilities when someone reminds him that he would have time for that after they figure out what's going on with the wererats. "Of course," he smiles. "I say we leave right away before our quarry makes their escape."

Jorin will casually inspect the building we think the wererat went into while Hildigrim is in the book store.  He's going to stand outside, as if waiting on his friend, and just visually inspect the area.

Drusk wishes good luck to the trio, while Pascal waves goodbye before returning to staff hiring (with Fanny nearby). Root raises a branch to salute Quillary, and you feel invisible hands straightening your clothing before you go out the doors.

It is a fine morning, especially after all that time in the darkness under the city.

You follow the street and head west.
(At other times in the past, you've sometimes gone east to visit the "Bent Nail" for carpentry service, or the "Steam and Steel" blacksmith shop.)
You pass "Corellon’s Crown" and get a friendly wave from Fala the herbalist.
You also pass the "Tiger's Eye" detective business, and see a pair of eyes watching your passage from a window with the drapes drawn. (Kind of like what Hildigrim did last night when the were-rat gang left.)

You arrive at the "Book Wyrm's Treasure". Jorin has to grab the back of Hildigrim's collar to keep him from continuing to march into the bookstore. Next door to the east is a smaller building. (Like most of the buildings on this alley, the first floor is business and the second floor is habitation. Your manor is one of the few with 3rd and 4th floors.) The exterior of the first floor shows signs of renovation, and the large sign over the entrance hasn't been completely painted yet. In large print is "Frewn’s Brews", with smaller print below: "finest pub in th..." (incomplete).

Hildigrim says that "finest" sounds like marketing speech, especially since they haven't opened yet.
(The repair work and painting looks cheap and second rate, compared to what you hired people to do for the Road's End manor.)

Quillary (in half-elven form still this morning, her magical armor taking the guise of regular, if patchwork clothing), stops in front of the bookstore, eyeing the building next door. She observes whether there is any activity at Frewn's. Workers, patrons, owners?

(This half renovated brew-slingery is where we think the wererat went in?)

No patrons, since the pub isn’t ready to open anytime soon. The building repairs are only partially done, like the workers walked away before they finished. Doors are closed, window shutters closed. You do hear a discussion inside, with frequent angry yelling. Kelso is one of the voices. (You haven’t heard the other 3 were-halflings talk, so you’re not sure about the other voices.)

Hildigrim grins and whispers, "Sounds like interrupting business renovations and making claims is their thing. I'm curious to know their motives." He pauses. "Shall I go in?"

Quillary nods, but says, “Remember, we are here to ask about the rats at the Road’s End. They may be jerk wererats, but that is their business, no?”

(OOC: If you want to listen to the conversation, you'll have to sneak up to the door and roll a Perception check as you put your ear against it.
You could stay where you are and try to listen in. Considering the street noise and the thickness of the door/wall, the DC would be a lot higher.
You could just walk in.
Or I wasn't sure if Hildigirm had some idea of somehow sneaking in that I hadn't considered.)

Quillary, much as she wants to barge in, is self-aware enough that she knows this is not the plan, so she is waiting for Hildigrim to suggest a course of action.

Jorin preferr the direct approach and says, "Aye Hildi, let us see what these rats are up to." and will follow him in if he goes in.

Hildigrim turns his back toward the building and casts invisibility on himself. Once out of sight, he will sneak up to the building to eavesdrop.

Stealth: 15 — advantage? 23

Perception: 14

Hey, DM: Because Hildigrim constantly feels like he's being watched and is now ignoring it, take that into account when deciding a DC or using passive perception (or another skill) that would involve him usually getting that feeling and paying attention to it. I'll let you decide the mechanic, but it's OK fair to penalize him.

Quillary blinks as Hildi disappears. “Well, I guess we are on our own, Jorin of the Bodt. Perhaps we should give him a moment to discover something before charging in? Tell me, I did not offend your people when I took the form of a wolf, did I?”

Hildigrim winks out of sight. Jorin and Quillary hear his footsteps going towards "Frewn’s Brews", but you soon lose track of where he is.

For Hildigrim only:

Jorin and Quillary wait 5 minutes, looking around at the shops to make their loitering a little less conspicuous. Then the front doors of "Frewn's Brews" open up. The 4 (wererat) halflings step out, looking grumpy. They close the doors behind them. They only take 2 more steps when Danika grabs Kelso by the shoulder. Before he can complain, she mutters out "there's something wrong here." She raises her face, and blatantly sniffs the air around their group.

(Jorin and Quillary have a chance to act. Or OOC consult with each other, but not with Hildigrim.)

(During the 5 minutes of shopping)

Jorin looks quizzically at Quillary saying, "The wolf is a great creature, powerful and steadfast.  You actions in his form did him honor.  Why do you ask?"

(When the wererats come out)

Jorin eyes Danik and laughs saying, "Indeed there is!  I had too much of a breakfast that did not agree with me and it is trying to make itself known once again."  He will then...let out a fart...and sheepishly grin.

Jorin marches up to the gang. They tense, ready for battle, but then Jorin laughs and lets one rip. Quillary was walking next to Jorin to support him, but at that terrible sound, was able to step back and upwind of Jorin. (She remembers what Jorin was eating the days before in those underground caves to supplement the rations. She has experience with troglodyte stench, but decides it is best to be away from Jorin.)

The halflings eyes are watering, and they gag in disgust. Quillary and Jorin notice 5 people coughing, but the 4 gang members are not aware of the extra voice. Shortly, they flee to the east. Still trying to regain his composure, Kelso sputters out "you'll pay for this" and continues running down the street.

(OOC: I am reluctantly forced to give DM-inspiration to Jorin.)

(Huzzah, inspiration!  Did i correctly deduce they were smelling the invisible Hildigrim?  I was reluctant to employ a fart joke/action, lol, but it seemed to fit the situation and, uh, totally in line with something Jorin would do)

OOC > I am completely impressed. I mean, I figured they were smelling Hildi, but I had no idea what to do about it. Inspiration well deserved.