This is the 61st novel published by the BBC to feature the 8th Doctor.  His companions are Fitz Kreiner and Anji Kapoor.

This story takes place just after the previous book in the series, Time Zero.  The Doctor and his companions arrive on the planet Selonart to discover that the yacht they landed on has been set to overload its engines and all of the crew have been slaughtered.  They find a "native" named Bloom and they escape just before the creature get them.  The TARDIS is washed overboard so they must use an escape pod.  They, of course, are blamed for the yacht's destruction and are taken into custody.  They escape but, in the getaway, Fitz and Bloom are separated from the Doctor and Anji.

Fitz and Bloom are press ganged onto a ship were Bloom bargains for Fitz's live in exchange for his services to the crew, which include the ability to "feel" the currents in the ocean.  The Doctor leaves Anji to persuade the governor to call of the race, which of course he won't.  The Doctor goes with some special forces to investigate the strange "ice" that has been forming.  They find that this is actually water that all of the molecules have simultaneously decided to take every possible outcome at once (i.e. all of the multiple universes compacted into one).

Sabbath is trying to use this to enable himself to alter the nature of the universe and compact it into the "true" universe.  Instead he is double-crossed by his allies, the Warlocks, and he is taken to their world.  The only outcome of the "ice" on Selonart is that the "natives" become one with the water and with time.

Innocence.  They did seem like children.  Wise children.  Had no one ever bothered to work out how they could look so different in just a few generations?  None of the Selonart here were as odd-looking as Bloom but they still stood apart.  You couldn't have mistaken them for any other race.
    I think I, along with everybody else, had been overlooking these people.  Certainly the fact that they knew of the existence of this hideaway meant there really was more to them than waiting at tables and washing up.
    Arken led me across to network of stone bridges to the largest clump of Selonarts.  The men, women and few children seemed content enough.  Many were actually bathing in the pools around the,.  The cavern rung with their oddly flattened voices.  Laughter, something I hadn't heard in a long time.  More refreshing than a vodka and orange.
    'Whalen,' said Arken.  A man turned.  Older, more like Bloom.  A scar ran livid and pink from temple to lips.  He smiled and again I was reminded of the worried giant we had met on the yacht.
    'You are Anji,' he said.  I didn't know if it was meant as a question.  'Friend of Bloom.'
    For some reason, I felt tears prick my face.  It had been a long time since I'd felt any words of real, unmediated kindness.  'Pleased to meet you, Whalen.'
    'Whalen, yes.'
    'Bad on surface,' said Arken.  'Stay for while.'
    Whalen nodded.  'Not much stuff for you, Anji.  But please stay with us.'
    Here I started crying for real.