"The Cathedral of Contemplation is an enigma, existing outside time. It turns through history, opening its doors across the universe to offer solace to those in need. Occasionally, the Doctor drops in – when he's avoiding his destiny, it’s an ideal place to get some perspective. Only this time he's already there from several lives earlier, so when dimension barriers break down, his past and present collide. And when the Daleks invade and commandeer the Cathedral, two Doctors must unite to stop them – or face extermination twice over!"
[ANALYSIS TO FOLLOW - (Doesn't it sound good, though?)]
The good news is that this is everything I hoped that a crossover between (arguably) the most popular Doctor of the classic era and (arguably) the most popular Doctor of the new era would be. It's a pretty straight forward "Doctor vs. Daleks" story, but the fun is in the interaction between the two Doctors. There are far too many funny quips to quote here; I'd have to transcribe the entire script! The Tenth Doctor knows who the Fourth Doctor is, of course, and it doesn't take the Fourth Doctor just too long to figure out who the Tenth is. Because [reasons], the Tenth Doctor has no memory of this adventure until it happens. He even coins a term for this phenomenon: apres deja vu. From the Fourth Doctor's point of view, this story takes place shortly after "The Deadly Assassin"; from the Tenth Doctor's, sometime between "Journey's end" and "The End of Time" when he's on the verge of regeneration.
The bad news is that the second part (of three) won't be out until June 2021.