Medea Jones is the younger cousin of Hestia Jones (HP canon character). During Medea's first year she meets and becomes friends with Barty Crouch Jr. Eventually their friendship matures into love. Medea's parents are Death Eaters and she is expected to become one as well. As Voldemort tries to lure her into his group, Barty Jr. becomes fascinated with the dark powers displayed by the Death Eaters and the approval and attention given to him by Voldemort. Barty and Medea are initiated into the Death Eaters, although Medea never takes her vow to heart. She loves only Barty and tries to temper his growing obsession with Voldemort. Events from the HP books are woven in and after Barty's first incarceration, Medea flees to travel the world and gain knowledge, hoping to become the premier alchemist in the wizarding world. When Medea learns that Barty had escaped and returned to Voldemort, only to be recaptured and given the Dementor's kiss, she plans a horrible revenge on the dark wizard she blames for separating her from her beloved as well as an unprecidented scheme to restore Barty.
Other Medea-centric ideas I'm planning to incorporate include the loss of two sons (one stolen, one miscarried) and a divine rescue via flaming chariot. Opinions and ideas welcome.