All the Doctor and Sam wanted to do was go to a wedding. Two of the Doctor's companions, Stacy the Human and Ssard the Ice Warrior, are getting married. They've picked a beautiful place for it too: an artificially constructed world called Micawber's World, built out of an asteroid.
Unfortunately, when the Doctor is involved, nothing ever happens as planned. To start with, the Wirrrn (yeah, the bubble wrap ones) are in the midst of invading Micawber's World. For another thing, the artificial world is playing host to the Olympic Games™. And for a third, there's this strange cult called the Church of the Way Forward protesting the interspecies wedding.
Shortly after Stacy and Ssard are happily sent off on their honeymoon, the Doctor begins investigating a number of these strange events. The investigation is made a bit more complex by the fact that even the ordinary Federation humans and aliens are double-dealing, lying, and generally causing trouble unrelated to the impending Wirrrn invasion. However, through a combination of asking the right questions, somehow managing to get on everyone's good side (practically a first for the Doctor), and knowing more than everyone else, the Doctor figures out what's going on.
Meanwhile, Sam investigates the Church of the Way Forward, gets into long religious debates, and generally doubts her own beliefs. She, as usual, ends up running into trouble, but this doesn't help the Doctor's investigation much, since he's already figured out what's going on by the time they're reunited.
By then, however, it already seems like it's too late.
Tropes present in Placebo Effect include:
- The Assimilator: The Wirrrn.
- Author Filibuster: The debate between Sam and Reverend Lukas seems awfully like one
- Continuity Nod: Stacy and Ssard are companions of the Doctor from a relatively obscure line of comic strips in the Radio Times. It's revealed in the story that the Doctor had those adventures while Sam was dropped off somewhere, but returned for her before she knew he'd been gone.
- Continuity Porn: Pretty much everyone in this book comes from some previous episode/book/comic.
- The Wirrrn (Ark in Space, but spelled with an extra "r" like in the novelisation of said story)
- The Foamasi (The Leisure Hive)
- Stacy and Ssard (Radio Times Eighth Doctor Comic Strip)
- A Meep (The Star Beast - Fourth Doctor Comic)
- Kleptons (Klepton Parasites - First Doctor Comic)
- SSS (The Daleks' Master Plan)
- The Federation (Curse of Peladon, Monster of Peladon)
- Also, The Eighth Doctor, it seems, is once again half-human. He can also tell details of random people's futures.
- Fantastic Racism: Sam is rather offended when Kyle says that all Meeps look the same.
- Fully Absorbed Finale: The Stacy and Ssard plotline wraps up the story of Russell's short-lived Radio Times Eighth Doctor comic strip.
- The Fundamentalist: Reverend Lukas and his Church of the Way Forward
- Interspecies Romance: Stacy and Ssard. The Church of the Way Forward takes issue with this.
- Shout-Out: Lots. All of the Foamasi use voice synthesizers based on 20th century Earth actors.
- The Foamasi who works in Room 101 uses a voice synthesizer based on Richard Burton, who played O'Brien in 1984.
- Another is John Gielgud, from Arthur 2: On the Rocks.
