Marc Fennell

The doctors and neighbors look around to see what could possibly have caused her this agony.

And then they notice something on the table.

Because it turns out that something was put in that beer that definitely should not have been there.

Now, prussic acid, you might know it by its more familiar name, hydrogen cyanide, which, if you've ever read Agatha Christie, is never a great sign.

It's a poison.

It's fast, it's brutal, and it stops your body from using oxygen.

So in effect, you suffocate even while you are still breathing.

In the ruckus, Sarah's neighbours spotted a man leaving her cottage when they went round to check on her.

And unfortunately for him, his fashion choices made him pretty memorable.

So who is it that chases after him to the train station?

Do we know that?

So if you want to picture what a telegraph machine was like at the time, it's less modern technology, almost looks closer to a handcrafted bit of furniture.

You've got a small device mounted on a wooden base.

There's exposed brass and iron parts and wires that are wrapped in cloth.

And then you've got this very simple metal key that you press by hand.

It's connected to a metal arm that moves up and down and sends short and long pulses and patterns, allowing operators to spell out messages

using Morse code.

It's a great little gadget, but at the time this is all happening, 1845, the general public didn't really get why they needed it.

The postal services in Great Britain had recently been made much easier and much cheaper, and the consensus seemed to be, why would you need a message to travel faster than a letter?

So the Slough train station master has just been told that there is a man on the train to Paddington that may have just murdered a woman.