Every year, the monarch butterflies—las mariposas—fly more than two thousand miles on fragile wings to return to their winter home in Mexico. Now Luz Avila makes that same perilous journey south as she honors a vow to her beloved abuela—the grandmother who raised her—to return her ashes to her ancestral village. As Luz departs Milwaukee in a ramshackle old VW Bug, she finds her heart opened by a series of seemingly random encounters with remarkable women. In San Antonio, however, a startling revelation awaits: a reunion with a woman from her past. Together, the two cross into Mexico to await the returning monarchs in the little village Abuela called home, but they are also crossing a border that separates past from present . . . and truth from lies.