At Deffry Vale school, the new headmaster, Mr. Finch (Buffy's Anthony Stewart Head), and his faculty have some very odd lunch habits, and the kids are getting smart on oily chips. But forces are aligning against the shape-shifting aliens that have taken over this school, including a new dinner lady named Rose and a new physics teacher named Doctor John Smith. With Mickey as backup, the two time travelers are about to make their move, but the Doctor might get more help from an unlikely source. Someone else has been investigating the school — an intrepid journalist named Sarah Jane Smith.

What was once the purview of fan fiction is now canon. By regularly returning to visit Rose’s mother and boyfriend, the new series has often shown us the ramifications of this unique lifestyle, but for the first time we see and feel the full tragic impact of what it means to see the universe with the Doctor and then get dumped back home to a life of mundane details and endless routine. The return of Sarah Jane is one of the most triumphant and melancholy moments in the history of Doctor Who, and it’s handled beautifully.

A still preternaturally stunning Lis Sladen returns to the role that made her a 1970s childhood icon, bringing with her the bane of the ‘80s Who production crew — K9 the super-intelligent robot dog, who traveled with the Doctor for several years and later joined Sarah Jane. Naturally the nostalgia factor here is off the scale, but it’s accomplished with such clarity that even newcomers can understand what this woman — and dog — mean to the Doctor.

Behind the plethora of continuity touches, and the Krillitane plot to unlock the secrets of the universe, lies the new series’ most powerful character study since “Father’s Day,” with the same tear-inducing results. Sladen and David Tennant have a wonderful rapport — their scenes are so charged with equal parts tension and affection that they virtually sparkle, and by finally exploring both Sarah’s true feelings for the Doctor, as well as his unspoken love for her and Rose, the episode opens up new but exciting emotional territory for the series.

Once again, though, Billie Piper is marginalized. Although this was touted as a story about Rose — the realization of what her fate might one day be when she leaves the TARDIS — she’s basically reduced to a sulking, bitchy child. The two women reconcile in a wonderful scene and their final farewell is touching, but Rose is ultimately ill-served by the episode, not the least by her final tantrum when the Doctor allows Mickey to officially join the TARDIS crew.

The slightly comical CGI Krillitane creatures have a lot of potential as future foes with their ability to adapt their appearance. And in Anthony Stewart Head’s Finch, we have everything the Doctor’s old arch-nemesis the Master used to be when Roger Delgado originally played the role. As the first truly malevolent match for the Doctor in this series, Finch is suave, seductive, animalistic, and well deserving of another appearance. He even offers the Doctor a share in the universe as the Master might have done, and only Sarah has the power to draw the Doctor back from the precipice by voicing a lesson she has only just learned herself — that all things pass, and life is about loss.

That the myriad plot threads of the Doctor and Sarah’s relationship, the Doctor’s loneliness and love for his companions, and the Krillitanes’ search for power should all be sewn up in one simple speech by Sarah is the episode’s crowning touch. The story is filled with eloquent dialogue, deft direction, and a propulsive score by Murray Gold. K9 even gets to be the hero! This was simply magic. Welcome back… my Doctor Who!

Next time, it’s French women and clockwork robots. Will the Doctor find true love, and will Rose pout like a little girl? Join me, won’t you? A