SOLVED. Dark YA book read in 2005- 2010ish. Spoilers ahead. [s]

[Baylee]

The mc moved with his family into a huge house complete with a pond/lake, a hedge maze, and a green house. One of the gardeners (I don't remember if they lived on the property or not) was trying to complete a spell on the solstice. The mc makes friends with one of the property workers son (he walks funny and the mc thinks it's because he is autistic who is also obsesed with Einstein) later in the book we find out that he walks funny because he has a key in his shoe. Sadly, that kid was drowned in the lake to cover up the spell work and he is a ghost.

[Becca]

The Hunt for the Seventh by Christine Morton-Shaw

[Baylee]

thank you so much !!!! ☺️ ☺️ that's exactly it!