Picking up on the same night as last season's finale, Elena arrives home to a nightmare as she discovers Uncle John's and Jeremy's fate. At the hospital, Sheriff Forbes is comforted by Matt, Bonnie and Damon while she waits to hear if Caroline will survive the car accident. After a confusing conversation with Elena about the night's events, Damon is the first to realize that Katherine has returned. Katherine's arrival sends Stefan and Damon on a path to find out what she wants, why she's back, and how much of a threat she is to the people they love. Meanwhile, still reeling from his father's death, Tyler is surprised when his charming and mysterious uncle, Mason Lockwood, arrives to console the family.

Elena, Damon and Alaric take a road trip to Duke University and search through Isobel's research on folklore and paranormal phenomena to see if they can uncover any clues to the mystery surrounding the Lockwood family. Isobel's former student, Vanessa offers to guide them through the research and ends up getting quite an education herself. Stefan comes face to face with a terrifying new danger in the woods, and Tyler makes a shocking discovery about Mason.