undead retribution

Mary woke up in a terrifying darkness, alone and cold. Her arms and legs were pinned tightly against her she could hardly move. "LET ME OUT "she cried " I CAN'T BREATHE"
Mary was finally getting to live her life, when it was all stripped away from her by one kiss from a long-time crush. "WAKE UP MARY" her best friend cried in vain! But it was too late Mary was DEAD!
Who is responsible? Will Mary get her retribution? OR MAYBE, MARY IS NOT DEAD AT ALL!