When on board H.M.S. Beagle, as naturalist, I was much struck with certain facts in the distribution of the organic beings inhabiting South America, and in the geological relations of the present to the past inhabitants of that continent. And then the dragons arrived.

"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.

The boy with fair hair lowered himself down the last few feet of rock and began to pick his way towards the lagoon. And then the dragons arrived. - Lord of the Flies, William Golding