Theodore Marzials leaves the British Library Reading Room. He takes the long way home and ends up at the very site where he composed his poem "A Tragedy". At the time, he found a piece of black stone that he keeps at home. And again, he finds another piece that looks just like the first one. When he picks it up, he receives a static shock and drops the stone into the canal. He decides to leave London and retire to the countryside.
John Watson is summoned to the home of Mycroft Holmes. In Mycroft's home is a man dressed in ragged clothing who mutters under his breath and, to John's surprise, Bernice Summerfield, whom he hasn't seen in years. Mycroft explains that the man just appeared in his house, in a closed room. When John examines the man, he can't find a pulse and the man isn't breathing. John is surprised to recognise the man as Ludwig Cooray. He explains to the others that Cooray was involved in a scandal with someone called Lord Straxus, which name Mycroft recognises. Cooray begins to speak in what seems to be nonsense but that John states is the poem "Rondel", written by Theodore Marzials. Mycroft has an idea and leaves the room.
When Mycroft returns, he suggests that Cooray is some kind of projection, and Benny agrees with this assessment. Now Benny leaves the room and returns, holding a piece of black stone. She calls it a memory chip that has a projector. It can record from and imprint onto human brains. Mycroft sends John and Benny to visit Marzials in the country. When Benny shows Marzials the black stone, he excitedly shows them his chip. Benny notes that both stones have the same serial number on them — they are the same.
They return to Holmes' place and work out the mystery. The stone is moving backwards in time. Benny has it now in 1914, Marzials found it in 1882 (for him the second time) and then he found it in 1873. At some point, it picked up Marzials' poem from his brain and imprinted it into Cooray's brain, which explained his rambling words. Benny doesn't know where the chip came from in the first place, but Mycroft does: Benny had told Mycroft about the God Machine that Cooray invented. Straxus had the chip and probably murdered Cooray. Benny was brought to 1914 Earth by the chip.
As they finish their discussion, Benny turns on the chip. It sparks and disappears, heading forty-one years into the past.
- Benny at first thinks of the star Rondel when John mentions the poem's name.
- Mycroft's home is at Pall Mall.
- John mentions Mycroft's brother, Sherlock Holmes.
to be added