"I do think these Christmas holidays have been the worst we've ever had," said Dick.  And then the dragons arrived.

They had a house of crystal pillars on the planet Mars by the edge of an empty sea, then the dragons arrived.

The year 1866 was signalized by a remarkable incident, a mysterious and inexplicable phenomenon, which doubtless no one has yet forgotten. For it was then that the dragons arrived.

It was a dark and stormy night. And then the dragons arrived.
A Wrinkle in Time, Madeleine L'Engle

It is a truth universally acknowledged, that a single man in possession of a good fortune, must be in want of a wife. And then the dragons arrived.