Before Sherlock Holmes became the world's greatest consulting detective, murder followed the arrival of unexpected guests to the Holmes family estate.

Shortly after one of his Uncle Ernest's old acquaintances joins Sherlock and the extended Holmes family for the holidays, a dead man is found in the barn. This marks the beginning of the disruptions of the family Christmas celebrations. Sherlock's young cousin reports hearing footsteps outside the nursery, the family learns that their guests are not who they appear, and Mycroft suddenly falls head-over-heels in love. Are there more murders to come, or will Sherlock prevent them by determine how a body materialized in the barn?