Dundas Boatyard is where the investigation into Sid Towers’s murder returns after the initial forensic work is over. Its towpath and canal become a temporary search ground, while the narrowboat’s fresh stern-door lock keeps the apparent locked-room problem at the center of Peter Diamond’s inquiry.

Setting and Return

Later the same afternoon, Peter Diamond drives Milo Motion to Dundas Boatyard so Milo can collect a change of clothes from his narrowboat. The crime-scene team has finished and left. As the sun disappears behind willows on the far bank, the clear sky threatens frost; only one constable remains nearby, rubbing his hands against the cold. The visit is practical, but it brings Diamond back to the place and boat around which the unresolved murder turns.

The Canal Search

Two divers are still searching the canal bottom for the weapon used to strike Sid Towers. The water is so shallow that their work amounts less to diving than to wading and bending double. After three hours searching fifty yards on either side of the narrowboat, they have gathered a horseshoe, two plastic milk crates, a bicycle pump, a birdcage, about twenty beer cans, and pieces of stone, laid out on a blue tarpaulin on the towpath. Diamond tells them to stop for the day. He doubts that a killer capable of such an artful crime would discard the weapon in an obvious nearby spot, but the search has been required as a matter of procedure.

Diamond also asks Milo to check whether anything aboard the boat is missing that could have served as the murder weapon. Milo cannot immediately think of such an object, though he agrees to look. The question makes the boatyard more than a backdrop: the narrowboat and its contents remain possible sources of evidence even after the formal scene examination has ended.

The Lock and the Unresolved Case

A constable has to open the boat because its stern door now carries a fresh lock. The German-made padlock previously fitted there has been dismantled and examined at the forensic laboratory. The investigators find no mechanical flaw and no sign of tampering; its close-shackle design offers more than six million key variations, consistent with the manufacturer’s claim that every padlock sold in Britain has a unique key pattern.

The technically sound lock deepens rather than resolves the mystery. Diamond has repeatedly considered the narrowboat’s security without working out how the body was placed inside. At Dundas Boatyard, the routine recovery of clothes, the abandoned weapon search, and the unexplained lock converge on the same obstacle: the murder of Sid Towers remains, for Diamond, a locked-room puzzle.