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.
When Dash discovers Lily didn't leave the notebook in their prearranged spot, he tries to track her down using the unique footwear she left behind.
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.