They had two leads to follow. One was the mud they found inside the room where Silas had been killed. That certainly came from the inhabited parts of the forest. Well, not inhabited like there was no one living there, but it had way less people as it was not safe like the city.
The other lead was the manager. Alex wanted to follow the manager to see what he was up to after the night kitchen workers said he was acting a little strange. But it was just a clue, something they want to check when possible. The mud inside Silas room was an accurate thing to follow first.
"The road so far is cobblestone," SwordSlash77 said after they left the city, "So where does this mud come from?"
They had stored the mud inside a flask — Alex always had many with them carrying blood, so it was easy to get an empty one.