Having destroyed his ship seconds before it was due to destroy Earth, the Doctor and Martha leave villain Baltazar adrift in open space assuming he will serve the rest of eternity in prison. Travelling forward in time they learn that he was in prison but was released as he was deemed "reformed". On the contrary, the Doctor learns that Baltazar seeks "the infinite", a device of great power that will see him able to be the scourge of the galaxy. The Doctor and Martha set out to recover it first, but is it part of a trap?
This animated Doctor Who episode was screened in parts over the series "Totally Doctor Who" which I never watched because it was aimed at children (as the title would suggest). However the complete special was trailed after the first part of the season 3 conclusion and, since I enjoyed that so much that I was in the mood for more. At first glance I didn't think this was going to be any good. What put me off right away was the animated Doctor and Martha just looked, well, odd. I didn't manage to get past this and even after 45 minutes I still thought that they didn't work visually but what did work well was the fact that whole episode was set in locations that even the increased budget given to season 3 couldn't have created. The locations are inventive and well laid out the animation isn't amazing but it is good for what it is.
The plot is reasonably good and allows for the location hopping and for, in theory, the creation of another nemesis for the Doctor (assuming the animation went on from this one-off). The voice work is not that great though. The presence of Tennant and Agyeman is a bonus of course but they don't manage to produce anything as good as they do in the series Tennant is a bit too wacky here though. Head has a good voice for his character but people like Liza Tarbuck, Calyton, Meo and Morgan stand out too much without giving good performances at the same time.
Overall then this is an OK special that will probably be worth seeing for fans but not for the casual viewer who would need it to be at the level of the "proper" series. Visually it offers locations beyond the budget of the normal series but the performances and characters aren't there with it.
