The Amaranth Maze. Arcana Europa

A legend of a long-dead murderer buried in a mysterious maze. A cruel, childish trick gone wrong. A dangerous vow made in trust by a shy and lonely young boy. And somewhere in the idyllic Swedish countryside, a centuries-old entity is summoned from its thorny grave. Fourteen years later, twenty-two-year-old Fredrik Niequist returns from his travels, a brilliant financier who intends to break new ground in the Swedish agricultural industry by commercializing local nature magic.
He is also newly engaged to a wealthy childhood friend in a cynical and loveless partnership. Twenty-year-old Lauris Ahlberg, meanwhile, turns his mind to botany as a promising apprentice to an English botanic occultist. As he studies a flower species displaying marks of the night world, he realizes the tainted flowers' sudden appearance near his home and the ominous pattern they form signify a terrifying presence coming from a familiar source.
When Fredrik and Lauris cross paths again, old wounds break open, and promises of forever after ring hollow as the two awkwardly rekindle their friendship. And in the meantime, a creeping threat takes physical shape, breaking past its prison of thorns in order to lay claim to what has long belonged to it.