The Ood have given a warning to The Doctor. The Master is returning yet that is not the biggest threat. A darkness is coming which brings with it The End of Time.

The Eleventh Doctor is portrayed by Matt Smith. Steven Moffat took over as head writer and executive producer after Russell T Davies stepped down. Julie Gardner also stepped down as executive producer and was replaced by Piers Wenger and Beth Willis.

When the hospital she works at is transported to the moon, medical student Martha Jones joins forces with The Doctor to hunt down an alien fugitive before the oxygen runs out

The Tenth Doctor meets one of his previous incarnations.

本集讲述博士和泰勒回到当代的伦敦渡过圣诞节。然而，外星人希克拉库斯（Sycorax）却在这时入侵地球。最终，因重生过后昏倒的博士及时醒来，击退入侵者。在英国，这集有980万人收看，并取得正面的评价。
这是扮演第十任博士的大卫·田纳特首次出演整部《神秘博士》剧集。此前，他在《背水一战》的最后一幕出场。同时，这是《神秘博士》首部的圣诞特辑。自此以后，BBC One每年均会制作一部圣诞版的《神秘博士》剧集。