The Rubbish Companion

[Set: pre-"Rose" Ninth Doctor, post-"The Crystal Cave" pre-"The Coming of Arthur"] All seems well when the TARDIS takes a wrong turn and ends us in the Middle Ages; Camelot is exactly the new adventure he's been looking for. However, a mysterious blue box appearing out of nowhere causes trouble, and soon local historical figure Merlin is dragged into an unforgettable escapade.