SCENE 1: INT. BLACKFRIARS SIGNAL BOX - MIDNIGHT

[FX: Wind howling outside over the River Thames. Ticking of a massive brass pendulum wall clock. Mechanical clanking of iron signal levers.]

SIGNALMAN HOLLOWAY: (to himself, checking pocket watch) 00:05. Thameslink cleared. Freight to Kent cleared. Nothing scheduled until the 04:12 to Bedford.

[FX: Heavy iron signal bell rings THREE slow, deep tones. DING… DING… DING.]

SIGNALMAN HOLLOWAY: (startled) Line three? Line three was decommissioned when they rebuilt the roof!

[FX: Low rumble of a steam engine approaching in the distance. The rhythmic CHUG-CHUG-CHUG of coal-fired pistons.]

SIGNALMAN HOLLOWAY: (frantic, grabbing brass telephone) Control? Control, this is Signal Box 4. I’ve got unauthorized steam traction on the down-fast line heading north from Elephant and Castle!

[FX: Telephone receiver emits static, then a woman’s voice humming a 1940s melody.]

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SCENE 2: INT. SIGNAL BOX - CONTINUOUS

[FX: The heavy wooden door creaks open slowly despite being locked.]

THE STRANGER: (quiet, polite voice) Cold night on the river, Holloway.

SIGNALMAN HOLLOWAY: (gasping) Who are you? How did you get up the ladder?

THE STRANGER: I bought a return ticket at St Pancras in January 1962. I’ve just come back to collect the change.

[FX: A brass passenger train whistle roars directly underneath the floorboards. Vibration rattles windows.]

SIGNALMAN HOLLOWAY: (terrified) The train… it’s stopping!

[FX: FADE OUT]