Our campaign has a large number of PCs (8) and we run side adventures to keep the PCs up to the level the adventure path. So they group went through 'A Night on the Town' side trek which appears in other posts in this forum. This occurs after the Whispering Cairn but before 3 Faces of Evil.
Chapter I: I changed the emphasis of that side trek. Thurbiss and his goons kidnap Constance Grace (see the Midnight Salute entry) because she is the paramour of Ragnolin Dourstone and knows too much. The PCs track Thurbiss and his guys to the dead hole mine and fight them and a priestess of Vecna. From the captives they learn Constance had been thrown down a pit where a dread monster lurks. They rescue Constance, and kill the Harpoon Spider. Finally they get a reward from Purple Prose.
Chapter II: During 3 Faces of Evil, 2 PCs die fighting the Grimlocks. 2 Replacements and Melinde the Heironean Paladin are contacted and hired by Constance Grace to protect her from Ragnolin Dourstone whom she fears.
Constance is kidnapped and carried off before the trio meet with her face to face. They see the kidnappers running off through a broken window and give chase. They find them going into the Dourstone Mine.
The trio eventually fight the evil doers as they are about to throw Constance into the Dark Pool from a high ledge. The bad guys include 2 kenkus, an apprentice of the Faceless One, a Lurking Strangler, and a cloaked and cowled Purple Prose. All are killed except Prose who surrenders.
As the fight ends the other group of PCs encounters them and they parlay.
Melinde and Constance take Prose prisoner and head to the surface to warn the Militia. Prose brokers a deal which allows her to head to Celene in exile from the lands of Greyhawk. She will be a prisoner of Ellival Moonshadow, the patron of the two elf PCs. The next silver shipment Ellival sends to Celene he will have Prose taken to the temple of Hanali the elven goddess of love and beauty for punishment.
Prose tells the PCs most of the backstory of the Ebon Triad, as she is an old and valuable agent of the Faceless One and pays lip service to Vecna.
One of the elf PCs loves to play the role of 'the Brilliant Planner' or 'Wheeler/Dealer'. He learns valuable information and later when the PCs find the Faceless Ones letter, he is invested in what is happening.
I have also played up the dire history between the elves and Vecna, who was a flannish human wizard who learned much from the elven kingdoms then destroyed much of the elven realm.
It should be interesting as they encounter agents of Dalt in the near future. Prose will also pop up again, repentant NN rather than NE. In time her survival will be important to the Age of Worms as the PCs will need someone to take up the relic Dalt possessed.