Jo, Benton and Yates are grumbling about Christmas when the Brigadier enters and assigns them to duties for the UNIT Christmas party. He sends Benton to the airport to pick up a guest, Doctor Aloysius Fischer, who especially wants to meet the Doctor. Yates is in charge of food and entertainment, and Jo will be the hostess. When the Brigadier tells the Doctor of the party, the Doctor refuses to attend, but grudgingly agrees to show up at the end of the evening.