Time Will Tell — Barry Lyga

A young-adult thriller ricocheting between the bigotry of the past and present as teens unravel their parents' secrets. Perfect for fans of One of Us is Lying.
 
Four teens have dug up the time capsule that their parents buried in 1986 and never bothered to recover. But in addition to the expected ephemera of mixtapes, Walkmans, photographs, letters, toys, and assorted junk, Elayah, Liam, Marcie, and Jorja discover something sinister: a hunting knife stained with blood and wrapped with a note. “I'm sorry. I didn't mean to kill anyone."
 
As the action dramatically alternates between the present day and 1986, the mystery unfolds and the sins of the past echo into today. The teens haven't just unearthed a time capsule: they've also dug up pain and secrets that someone -- maybe one of their own parents -- is willing to kill for.