The Cobalt Lens

The cold open

Rain slicks the skylight of a rooftop optical laboratory twelve floors above the midnight avenues. Beneath the brass armature of an eight-foot equatorial refractor, a man lies sprawled across the parquet floor with a single bullet wound through his monogrammed linen waistcoat. The smell of gunsmoke lingers faintly beneath the sharper tang of lens polish and optical resin.

The victim

Tobias Mercer, 54, master precision optical engineer and bespoke telescope maker

The lineup

• Kellan Rowe
• Therese Lin
• Milo D'Souza
• Astrid Holm