Our Doctor Who superfan Lizo reviews the fourth episode of the fourth series - The Sontaran Stratagem.
Called back to Earth by Martha Jones, The Doctor and Donna are investigating mysterious ATMOS devices, which are attached to half the cars on the planet to make them more environmentally friendly.
But why are the workers at the ATMOS factory behaving so oddly? And how is an institute for young geniuses involved?
The Doctor isn't sure. But he does know that there's trouble in store when he comes face to face with alien race the Sontarans.
The big attraction here is the return of Martha Jones, who fills in a few blanks about what she's been up to since she and The Doctor parted at the end of the last series.
She's now working for an organisation called Unit which investigates alien threats.
And we also get to find out a bit more about Donna's family, one of the great things about Doctor Who is that we don't just follow The Doctor around on his adventures, we see how it all affects his companions' home life back on Earth.
The combination of The Doctor, Martha and Donna together for the first time promises a lot, and delivers with a good old fashioned adventure.
And a great alien threat in the Sontarans - think Judoon, but with fewer horns and more aggression.
It's the first of a two-part story, so there are a lot of things set up which won't be explained until the next episode The Poison Sky.
But it manages to be an exciting, fast-paced 45 minutes which, while not as emotional as the last two episodes, keeps up the superb momentum that this fourth series has had so far.
Four out of five.
"This was a really good episode but I thought it would be scarier. I thought it was going to be a bit rubbish, but I was gripped by the end. Is it me or does David Tennant look older?"
Sarah, 10, Hatfield, England
"I loved Doctor Who, I always do and I want to skip this week and find out what happens to Donna's dad and if the doctor can stop it. I hope so. I want to know if Martha can save herself (finger's crossed)."
Ozi, 10, West Sussex, England
"I think episode four was absolutely fantastic. I loved the chant at the end, SONTARAN! SONTARAN! SONTARAN!"
John, 13, Wexford, England
"I think it was a great idea to bring the classic monsters back and truly the best episode so far in series four."
Kane, 11, Manchester, England
"A FANTASTIC episode, the graphics were brilliant but my favourite bit is when the doctor confronts General Staal. The doctor is so cheeky. There are many things I like about the episode, 5/5!"
Samuel, 11, Luton, England
"I think that this particular episode was rubbish! It was too science fiction. Since Catherine Tate has taken over it has been rubbish!"
Elsie, 11, Hampshire, England
"I thought Doctor Who was brill. I don't know how the Doctor's going to save everyone now."
Lydia, 12, Nottinghamshire, England
"Amazing! A great episode. It was yucky when the clones came out of the green water!"
Amy, 11, Watford, England
"I think Doctor Who was really good on Saturday. I can't wait for the second part."
Hannah, 11, Wrexham, Wales
"I thought the episode was quite cool but I really can't wait for Rose to return. I think Martha is awesome but she has become bossier!"
Ramla, 13, Sheffield, England
"I thought this episode was interesting but it wasn't the best so far. The effects were great and I loved the plot, but some parts I didn't understand first time and had to rewind to get what was going on. But overall it was fab!"
Kirsty, 10, Paisley, Scotland
"A truly amazing episode. Everything about it was just so perfect. I can't wait for next week."
Sean, 13, Manchester, England
"I think that this episode was sooooo cool! I liked it when Martha came back, but I didn't like it when they put Martha in the gungy stuff. Really scary."
Laura, 10, Rochdale, England
"I thought it was a brilliant episode but Catherine Tate acted much better than Freema. It was very exciting and fast but not very scary. Roll on next week!"
Jimmy, 10, Bishop Stortford, England
"To be honest I thought Donna and Martha were going to pull each other's hair out, but I was shocked when they got on well. I do hope that Wilf gets out OK."
Sophie, 13, Birmingham, England
"I thought the episode as a whole was fairly successful. I would have liked to have seen a rift between Donna and Martha though."
George, 13, Lincolnshire, England
"The Sontaran Stratagem was very thrilling, with all the action going on in ATMOS, and at the Rattigan Academy. The Sontaran costume was very good as well, and the blue suited them. I am bursting to find out what all the poisonous fumes coming from the cars will do to the atmosphere in The Poison Sky."
George, 10, Harlow, England
"I loved this week's Doctor Who! It was great with the Sontarans, Martha, Donna, the Doctor, and the Doctor's cheeky attitude towards the aliens. It was great, but it was also a bit scary!"
Katie, 10, Manchester, England
"Personally I was disappointed with Martha's return. I thought she was hardly in it and I preferred her character in the last series. It's a shame because I thought she was much better than Rose but in this episode Donna way out shined her."
Elly, 13, Oxford, England
"I thought it was OK but it wasn't very gripping and needed something more, like a sighting of Rose or something.
But I thought Donna's family were so funny! 4/5 stars."
Kate, 11, Leeds, England