Some Rats Don't Fall For That One

There's a lot of fine stuff in the Scout Law. A Scout is to be trusted, for example. That's a good all-round rule to live by. A Scout has courage in all difficulties - it never hurts, does it? Nonetheless, I feel that there's one crucial point that's missing, and that ought to be tagged on the end as soon as is possible. Something along the lines of "A Scout has something other than lukewarm porridge between the ears." Now, brace yourself, you may have to read the following sentence twice.

Last night, one of my Scouts tried to wash the dishes with rat poison.

Now, just put yourself in his shoes. You're stood in a building which has had a rat problem. You are washing up, a task for which you have all the relevant equipment, some of it in a clearly labelled bottle. In a drawer, in the unit through which the rats had been scrambling, you find two trays of tiny, mysterious blueish-green pellets. These trays have the word "Rentokil" set into the side. By what possible feat of reasoning do you conclude that it would be a good idea to add them to the bowl?

Last night, one of my Scouts tried to wash the dishes with rat poison.

(Told you you might have to read it twice.)