The Titanic is doomed – because it’s going to collide with the anti-Titanic from an alternative universe and like matter and anti-matter colliding… well, the explosion caused by those two masses coming together could rip the Earth’s mantel apart.
Dr. Who is forced to make a terrible choice… with disaster imminent an iceberg seems to be the only way to avoid disaster, but who does he choose to live and who has to die?