The destination, Lower Hogsfield, is a small village located on the south side of the world map. It is far from Hogwarts. The nearest shortcuts are from either the Bell Tower Courtyard or the North Gate of Hogwarts.
Collect equipment from the pumpkin hut
On the way to Lower Hogsfield, there is a house with a pumpkin field where you can pick up the "Mottled Brown Ensemble" and the "Invincible Quidditch Gloves." These are useful equipment that can easily boost your stats, so it is recommended to collect them.
Talk to Natty, who is near the shortcut in Lower Hogsfield, and listen to the conversation about the incident involving Harlow and Lockwood and the future investigation plan. Once the conversation is over, the quest is completed.
Crossing the Waters to Complete Trials of Merlin
To proceed with the story walkthrough, it is essential to clear the Main Quests: Herbology Class, Potions Class, and Trials of Merlin. Trials of Merlin Quest occurs after crossing the waters near Natty, so let's clear it while we're at it.
However, it is not necessary to complete the similarly named side content Merlin Trials scattered throughout the entire map. Just clearing the main quest, Trials of Merlin, is enough to trigger the story progression.