Doctor Who: Return of the Companions

It hasn't happened in 25 years: practically all the companions, past and present, ganging up to help the Doctor. And even then, in "The Five Doctors," the reunion of companions was incidental to the gathering of all the Doctors.

But the big news about the two-part Doctor Who season 4 finale, "The Stolen Earth"/"Journey's End" (airing Friday, July 25 and Aug. 1 on Sci Fi), isn't the casting. The episodes are a twist-packed culmination not only of season 4 but of plot threads stretching back to the beginning of the series – and beyond, with roots and links to 1970s Doctor Who. This is edge-of-the-seat stuff with lots of closely guarded secrets queued up for revelation. (Check out our image gallery for the two-parter here.)

It is fun to talk about the return of so many familiar faces. It's actually a kind of family reunion of the Doctor Who franchise. The Doctor's past and present companions are joined by the leads from its two spin-offs, Torchwood and The Sarah Jane Adventures, in what amounts to a tribute to outgoing executive producer Russell T. Davies. Davies is largely responsible for engineering the stunningly successful return of Who and accomplishing what no Who producer had been able to do before – generate successful spin-offs. The splashy finale feels like a party for the show's beloved mastermind.

Of course, the Doctor can't have a party that doesn't rapidly degenerate into mayhem. In the two-parter the Doctor and company face off against Daleks – only whereas last time the Daleks were greatly weakened survivors of the Battle of Canary Wharf, "The Stolen Earth" finds the Daleks – led by the last survivor of the Cult of Skaro, Dalek Caan – reempowered and an almost unstoppable threat to our entire planet. Fittingly, the action returns to New York, the scene of the Daleks' ignominious defeat in last season's "Daleks in Manhattan"/"Evolution of the Daleks" (3x04-3x05). And behind the Daleks is an even more dire threat (whom I won't reveal here for the benefit of those who wish to be surprised).

Joining the Tenth Doctor (David Tennant) and Donna Noble (Catherine Tate) for the finale are the essential ex-regulars from the new series: Rose Tyler (Billie Piper), her mother Jackie (Camille Coduri), and Mickey Smith (Noel Clarke), all returned from the alternate Earth to which they were relegated in the season 2 finale, "Doomsday" (2x13), and Dr. Martha Jones (Freema Agyeman), the season 3 companion, since attached to the UN alien-response organization, UNIT.

Also on board is another ex-companion, Captain Jack Harkness (John Barrowman), and the surviving cast of his spin-off, Torchwood: Gwen Cooper (Eve Myles) and Ianto Jones (Gareth David-Lloyd). Sarah Jane Smith (Elisabeth Sladen), an ex-companion from the days of Classic Who and the start of the younger-audience spin-off The Sarah Jane Adventures, is here as well, along with her friend Luke (Tommy Knight) and computer Mr. Smith (voice of Alexander Armstrong).

And there are other blasts from the past, including ex-prime minister Harriet Jones (Penelope Wilton), last seen in "The Christmas Invasion" (2006), now in dire trouble of her own. In a definite first, all three female companions are seen with their families. And there's another strange synergy: Bernard Cribbins, who plays Donna's grandfather Wilf, has already seen the Daleks invade our world – he co-starred in the Peter Cushing film Daleks: Invasion Earth 2150 AD (1966). The red color-scheme for the Dalek commander in this episode is a reference to the Cushing Dalek films, in which the Daleks appeared in candy-colored varieties.

And there are still more notable guest stars, including Paul O'Grady, better known in the UK for his drag character Lily Savage, and science writer Richard Dawkins, who happens to be married to ex-companion Lalla Ward.

The Who finale generated 7.4 million viewers in the UK when it was aired earlier this month. The viewership was fueled in part by (false) speculation that the crisis that develops in "The Stolen Earth" cliffhanger would result in the Doctor regenerating, meaning that David Tennant would leave the show.