At last he emerged carrying the square packet which his friend had obtained at Sydenham, and behind him also came Winsloe. They walked across St. James’s Square and up York Street to the Trocadero, where, after having a drink together, they parted, Winsloe going along Coventry Street, while his companion, with the packet in his hand, remained on the pavement in Shaftesbury Avenue, apparently undecided which direction to take.

I was standing in the doorway of the Café Monico opposite, watching him keenly, and saw that he was evidently well known at the Trocadero, for the gold-laced hall-porter saluted him and wished him good-evening.

A few moments later he got into a cab and drove away, while in a few seconds I had entered another cab and was following him. We went up Shaftesbury Avenue, turning into Dean Street and thus reaching Oxford Street opposite Rathbone Place, where he alighted, looked around as though to satisfy himself that he was not followed, and walked on at a rapid pace up Rathbone Place, afterwards turning into many smaller thoroughfares with which I was unacquainted. Once he turned, and I feared that he had detected me, therefore I crossed the road and ascended the steps of a house, where I pretended to ring the door-bell.

He glanced back again, and finding that he was not being followed increased his pace and turned the corner. I was after him in an instant, and still followed him at a respectable distance until after he had turned several corners and was walking up a quiet, rather ill-lit street of dark old-fashioned houses, he glanced up and down and then suddenly disappeared into one of the door-ways. My quick eyes noted the house and then, five minutes afterwards, I walked quickly past the place.

In a moment I recognised the doorway as that of the house with the fatal stairs!

Returning, on the opposite side of the road, I saw that the place was in total darkness, yet outwardly it was in no way different to its neighbours, with the usual flight of steps leading to the front door, the deep basement, and the high iron railings still bearing before the door the old extinguishers used by the ink-men in the early days of last century. I recognised the house by those extinguishers. The blinds had not been lowered, therefore I conjectured that the place was unoccupied.

The street was, I found, called Clipstone Street, and it lay between Cleveland Street and Great Portland Street, in quite a different direction than that in which I had imagined it to be.

After a quarter of an hour Parham emerged without his parcel, closed the door behind him, and walked on to Portland Place, where, from the stand outside the Langham, he took a cab to Lyric Chambers, in Whitcomb Street, opposite Leicester Square, where I discovered he had his abode.

My heart beat wildly, for I knew that I was now on the verge of a discovery. I had gained knowledge that placed the assassins of Eric Domville in my hands.

I lost not a moment. At the Tottenham Court Road Police Station I was fortunate in finding Inspector Pickering on duty, and he at once recognised me as the hero of that strange subterranean adventure.