From the Introduction to the Adventure:
The characters have been hired by the villagers of Liam’s Point to find the whereabouts of the orc raiders that have been causing untold damage to the area. The village and the surrounding villages have gathered a militia capable of combating the orcs, but since the orcs raid carefully in hit-and-run attacks, the militia can never land telling blows. By the time the defenders’ forces have reached one place, the orcs have attacked another area.
What the alliance of town needs is a group of scouts intrepid and hardy enough to find the orcs’ home base. The adventurers are given a clockwork dove which they are to use when they confirm the orcs’ home base. The dove will work as an Animal Messenger spell and deliver the message to the militia chief, setting up the climactic confrontation between the militia and the orc raiders.