Things make a lot more sense when you realise this was written by Jim Mortimore, who also wrote BF's 'The Natural History of Fear'. A lot of it is just... atmosphere. Nightmare vibes. Complex questions are presented, pushed around and not really answered, the setup makes less and less sense as more is revealed, and I'm not sure any of the characters really learned much of anything. Mixed metaphors, the book. A lot of the discussion is based around life and death, responsibility, and parents and children. The paternity/maternity bit was, for me, used interestingly to explore Sam and the Doctor's relationship. 

Well, the more I think about the book the less I like it as a story, but, as I said, vibes. I liked the vibes.

Sam was a whole character for most of the book, until she's possessed once more, and it's revealed she had actually been used by the aliens even before that. But in the beginning of the book, probably up until she gets the first telepathic message, it was all Sam acting on her feelings. 

Sam and the Doctor's first conversation in the TARDIS beach already starts setting up the question: does Sam want children? She's always tried to act more mature, capable, wiser than her age, and now she really is an adult; it makes sense for this idea to start popping up. She's still a very young adult though, in the threshold between fully mature (which in her mind is connected to being responsible for another's - a child's - life) and being a child herself. She wants maturity, respect, but is scared of responsibility. She wants to be done with child Sam, Sam who needs rescuing and protecting, but she does need rescuing and protecting a lot of the time. Obviously, the Doctor is her opposite: he has the age, the wisdom, the capability. He can handle the responsibility (we know this, Sam knows this), even though she sees him as irresponsible. He acts like a child on purpose ('a rich kid with too much money and no common sense, abandoned by irresponsible parents to amuse himself at the expense of the local townsfolk'), but he is, for all intents and purposes, her dad: the one responsible for her, the one who will come to her rescue, the one that will fix things for her. She knows he often sees her like that, like a child he's taking care of, raising, even, and resents him for it, because he's not her dad. 

Their relationship ping pongs between so many things between these books. They are friends, she had a massive crush on him, but it's now a platonic love with a smudge of 'if he ever wants to, I'm game'; he's her father-figure, her tutor, showing her the Universe so she can grow up and learn. She wants to be on a more equal footing, more like a team of two adults, and he does play along a lot. However, it can come off as patronizing, and it just makes her, immaturely, lash out like a kid. Their messiness is what makes these companion relationships interesting. All that being said, though, it does feel out of place, like it should have happened before. People say she’s acting too much like a teenager again in this book, but I don’t think we saw her as a grown up much after ‘Seeing I’ anyway. However, yes, I do believe this type of story would have worked better if it was right after 'Seeing I', or 'Placebo Effect'. Maybe even before the ‘Lost Sam’ arc? Not sure.

Sam has even more going on, though. She meets Saketh, a guy that can’t die and can make you also not die if you participate in a literal perversion of the Holy Supper (‘eat of my flesh and drink of my blood’). She also meets Delani, who’s a priest for a death worshiping cult. The question of choice and the role of religion is brought up a lot, along with the role of religion in shaping people’s choices and beliefs. So we end up with this theme: when you accept responsibility for someone, you are held accountable for the choices you make for them; what right do you have to decide if they should live or die based on your own beliefs? This comes to life quite clearly in Sam's nightmare where she runs over a child, who dies because her father, a Witness, does not allow for a blood transfusion. When Saketh offers her eternal life and his power, she’s terrified: it’s the ultimate position of responsibility for another’s life. She can save everyone if she accepts, but it will take away their right to choose. Sam herself fights the whole time for her right to choose, it’s one of her defining traits (one of the few, thanks to the way she’s characterized in these books). In the end, she accepts the power, and uses it to its max. This is when I get a bit lost: at what point do the nanites, the alien source of Saketh’s power, take over? How does that undermine her choice? 

The Doctor is turned up to 11 in this book. Literally, actually: he is acting a lot like Eleven at his ditziest, most manic. Flanderized, really, like Bugs Bunny or something. Not that Eight isn't flighty, he is, but he's usually more contained, a lot more refined, more logical, less of a babbler for the sake of babbling. He is entertaining, I’ll give you that, but the Doctor in a situation where millions of people will be saved if he can get to the TARDIS will make his point very clearly and seriously to get people to help him. Why on Earth did he let that nurse sedate him??? Looney Tunes Doctor was a weird choice, given the mavity of the situation the Bel system is in, another case of “Our Star is being Weird”. 

Like Sam, he’s faced with the morality of choice in the form of his right to interfere with alien affairs. Should he decide for these alien races what the right thing to do is? Again, there are billions of lives at stake, including the life of the baby planet thing and of the ancient Hoth. To explain the situation to him, the aliens (the Hoth, I think? This was a bit confusing) send him a telepathic dream as well. In the dream, he’s pregnant (wowzers), gets a C-section (wowzers) and the baby is put in an incubator that is a star. This scene altered my brain chemistry. He says ‘love you’ to the baby??? He wakes up completely disoriented asking where his baby is? Holy crap. Anyway, people are dying by the billions in this book because the sun is an incubator for a gigantic alien planet baby. It's a 'Kill the Moon' scenario, except it's the sun, and there are a lot more factors to consider. 

At this point in the story he’s calmed down a lot from his Looney Tunes antics in the first part of the book, which I appreciated. He just wants to get Sam and get the hell out. Sam’s corrupted by the nanites, “saving” (infecting) everyone she comes across. They talk, the Doctor and this Sam-shaped vessel for the nanites. He decides in the end to not interfere, to let the nanites try to do their plan: let the baby planet be born, use the gravity stabilizers he built to stabilize the star afterwards. There’s just too many races with their own reasons and rights for him to be able to push them to any decision that isn’t unilateral, and really, physically, there’s nothing he can do anyway. He just asks for Sam back; she is, after all, his base responsibility. If he can save only one person, it has to be her. The ending (how did they get to the TARDIS, I wonder?) is quite ambiguous. He’s moody, Sam’s not sure if she’s back to being herself or not. A lot of people died, but not everyone, and that’s that.

Structurally, this book is a mess. Characters teleport from place to place, there are way too many planets (if I might add, it's impossible for 23 planets in the same star system to be in the habitable zone). But I was engaged from start to finish. The dream sequences were fantastic, and the moral questions were compelling. Sam, while maybe acting too young for her 21-22 years, got some emotional development. It’s one of those stories where the Doctor doesn’t really “win”, because there is not an easy solution. In the end, I did like it. It was trippy in the way Doctor Who can’t afford to be on TV, and that’s why I’m on this ride.