Solace of Slytherin; a grandson of Voldemort Story

When Will, Nico, and Hazel leave for Europe to investigate on an amnesiac satyr and his missing half-blood ward, they didn't expect to come across something magical. Will would call it ominous, Nico would call it annoying, and Hazel would call it weird, but when the goddess of magic smiles really sweetly and bribes them with magic supplies, street cred, and the soul of an annoying immortal wizard, the trio must remain for a whole year to find the other half-blood, bury another half-blood, and keep another half-blood from dying.

Hecate implores them to think of it as a...vacation. And they get to learn about their ancestry too! How educational!

Meanwhile Harry is plagued by strange occurrences after the death of Cedric Diggory, and it gets stranger as three new students stay in Grimmauld, and eventually in Hogwarts. Is part of that strangeness because one of them happened to be the Slytherin grandson of the evil dark lord who he didn't even know was...capable of continuing the bloodline? Can Harry trust his friends? Trust these strangers? Trust himself? Or will he succumb to what hides in the shadows?