"I should have, if you hadn't started disparaging my headgear. I repeat, it was a hat of unusual elegance. It had a personality of its own."

"But it wasn't your hat we were discussing."

I sighed.

"All right," I said wearily. "It wasn't. Have it your own way. Some other fool followed a silver-grey Homburg twice round the Park this morning. Some other fool——"

A little gasp interrupted me.

"But how did you know my number?"

"I didn't. I don't. I never could have been about to should. Negatives all the way. It's just chance, my dear. Chance with a Capital J—I mean C. D'you mind if I smoke?"

Her reply was preceded by a refreshing gurgle.

"Not at all," said my lady. "D'you mean to say you chased us all that way?"

"Further. And if it hadn't been for that fire-engine——"