He struck furiously at his tormentor with his free hand, but Nap, by some trick of marvellous agility, evaded the blow.

He leapt over the back of the settee with a laugh of devilish derision.
And, "Bertie, go!" said Lucas peremptorily.
Without a word Bertie checked himself as it were in mid career, stood a second as one gathering his strength, then turned in utter silence and marched away..