The Slate Mortise

The cold open

Midnight rain glazes the cobblestones of St. Jude's Mews outside the frosted basement windows of the Crown & Cushion. Inside the private members' salon, beneath green enamel pendant lamps casting pool-table glare onto mahogany rails, Cosmo Eldridge sits impaled against his workbench. A heavy triangular mortise knife is buried straight between his ribs, pinning a ruined ledger to his chest in a dark, widening stain across the green baize.

The victim

Cosmo Eldridge, 54, master cue artisan and proprietor of the Crown & Cushion Billiards Club

The lineup

• Hugo Navid
• Saffron Varma
• Declan Brauer
• Minerva Geller