Hidden Rooms by Kate Michaelson

When murder hits home.
Long distance runner Riley has been fighting various bewildering symptoms for months, from vertigo to fainting spells. Worse, her doctors can't tell her what's wrong, leaving her to wonder if it's stress or something more threatening. But when her brother's fiancée is killed-and he becomes the prime suspect-Riley must prove his innocence, despite the toll on her health.
As she reacquaints herself with the familiar houses and wild woods of her childhood, the secrets she uncovers take her on a trail to the real killer that leads right back to the very people she knows best and loves most.
For readers who enjoy Deer Season by Erin Flanagan, All Good People Here by Ashley Flowers, and A Flicker in the Dark by Stacy Willingham.