Dash hates Christmas, but his Yuletide spirits brighten when he finds a mysterious red notebook filled with clues hidden at his favorite bookstore.

Lily loves Christmas, but the prospect of a lonely holiday inspires her to connect with Dash through the notebook — and send him on another dare.

After Lily shares the memory of her worst Christmas ever, Dash devises a late-night challenge that pushes her far outside her comfort zone.

As Dash and Lily forge a deeper connection with dares involving mochi and a Muppet, they deal with past heartbreaks and family issues.

Real-life distractions complicate Dash and Lily's letter-based relationship when they both decide to attend a holiday party with other people.

Lily's problems pile up after a dreary Christmas morning and an enlightening pun lead her to question everything she knows about Dash.

With the year's final hours ticking down, Dash does some soul-searching and comes to a decision about Lily, unaware that her life is about to change.