The BBC Press Office has released the official synopsis for The Wedding of Sarah Jane Smith, The Sarah Jane Adventures episode where for the first time the character of the Doctor will appear in a spin-off.
David Tennant of course reprises the role of the Doctor.
Sarah Jane has met Peter Dalton and wants him to become part of her life, as the adventure series continues; perhaps he could become a father to Luke. But Clyde suspects that Peter is hiding a secret or two, especially when he and Rani find an empty house where Peter says his home should be.
The Doctor makes a spectacular return on the happiest day of Sarah Jane's life but a deadly trap is awaiting them all.
As the strands of a clever and careful plan come together, can even a Time Lord save Sarah Jane on the day of her arch-enemy's greatest triumph?
The Doctor joins the battle, as the power of the Pantheon Of Discord grows in strength, in the second and concluding part of this week's story, but a deadly trap is waiting for them all.
The Doctor makes a spectacular return on the happiest day of Sarah Jane's life, but is he too late to save both his old companion and Earth itself? As the strands of a clever and careful plan draw together, the two friends are separated across different time zones and must fight to save each other. For one, there's a terrible price to pay.
Sarah Jane Smith is played by Elisabeth Sladen, Peter Dalton by Nigel Havers, Clyde by Daniel Anthony, Rani by Anjili Mohindra and The Doctor by David Tennant.
Part One will air on BBC One on Thursday 29 October and part Two will follow the next day on BBC One on Friday 30 October.