passing through Miss Lytton's room. 'What's wrong?' I asked as I
carried her along. 'I took some of that,' she replied, pointing to
the bottle on the dressing-table.

"I put a small quantity of its crystal contents on my tongue. Then
I realised the most tragic truth of my life. I had taken one of the
deadliest poisons in the world. The odour of the released gas of
cyanogen was strong. But more than that, the metallic taste and the
horrible burning sensation told of the presence of some form of
mercury, too. In that terrible moment my brain worked with the
incredible swiftness of light. In a flash I knew that if I added
malic acid to the mercury - per chloride of mercury or corrosive
sublimate - I would have calomel or subchloride of mercury, the
only thing that would switch the poison out of my system and Mrs.
Boncour's.

"Seizing her about the waist, I hurried into the dining-room. On a
sideboard was a dish of fruit. I took two apples. I made her eat
one, core and all. I ate the other. The fruit contained the malic
acid I needed to manufacture the calomel, and I made it right there
in nature's own laboratory. But there was no time to stop. I had
to act just as quickly to neutralise that cyanide, too. Remembering
the ammonia, I rushed back with Mrs. Boncour, and we inhaled the
fumes. Then I found a bottle of peroxide of hydrogen. I washed out
her stomach with it, and then my own. Then I injected some of the
peroxide into various parts of her body. The peroxide of hydrogen
and hydrocyanic acid, you know, make oxamide, which is a harmless
compound.

"The maid put Mrs. Boncour to bed, saved. I went to my house, a