He might have been a man in a trance.
And then very suddenly the spell was broken.

For no apparent reason, he fell headlong from his heights and burst into a merry little jig that set Gracie dancing like an elf.
He became aware of her then, threw her a laugh, quickened to a mad tarantella that nearly whirled her off her feet, finally ended with a crashing chord, and whizzed round on the music-stool in time to catch her as she fell gasping against him.
"What a featherweight you are!" he laughed.

"You'll dance the Thames on fire some day.

Giddy, what ?" Gracie lay in his arms in a collapsed condition.

"You--you made me do it!" she panted.
"To be sure!" said Piers.