As self-professed science sleuth Anne Gray entered the primary classroom with an intriguing array of equipment, designed and produced by herself, we had no clue what wonders the next hour and a half would reveal.
"I am going to tell you an imaginary story about a river," she told the P6 class. All ears and eyes were immediately directed her way - and I mean all.
The introductory story, which could easily be a real scenario, described three factories built on a river bank and bringing employment and prosperity to the town. Each factory had a waste pipe leading into the river and, as the waste in the holding tanks was always tested to ensure that it was safe before being released, there had never been any problems.
One day, however, a fisherman noticed dead fish in the river near the factories and some children who had been bathing there became very sick.
The river had become toxic. One of the three factories, which Ms Gray named AI, CUG and KL, had to be the culprit, but which one?
Thus the scene was set for a remarkable science investigation to be carried out by the class.
Dividing the children into three groups, Ms Gray gave each child a rack of four test tubes and a pipette. Each table was given tubes of solution representing the waste from one of the factories, four drip-bottle indicators to colour test the samples for acidity and a plastic container for waste.
The organisation and preparation of the lesson was superb, so the children carried out the experiment with remarkable skill and precision for ones so young. Each group tested all three samples, recording the colour changes on a simple tick sheet, after collaborating and agreeing on their results.
Ultimately each group tested a sample representing the toxic river water, comparisons were made and the guilty factory was identified.
A solution to the problem now had to be found. Ms Gray asked the hostile townsfolk (alias P6A) for suggestions. After cries of "Close it down", "Bulldoze it" and "Flatten it", she cleverly opposed their protests.
"Ah, but you see, this is a very important factory. It is the only one in the world making a solution which saves some sick babies from a lot of pain.
"Scientists should never be destructive, so let's have some constructive suggestions."
Guided towards a satisfactory solution, the class decided that the best course of action was to neutralise the acid in the waste, as this was what was causing the problem.
Ms Gray demonstrated the neutralisation of acetic acid (vinegar) by adding an alkali (baking soda), changing the colour from red to green. Then the children completed their own experiments, neutralising the acidic water.
Impressively, some of the children noticed that the waste in the container on their table was also red and insisted on neutralising it before pouring it down the sink, for fear of contamination.
As it was still a mystery to the children how the waste, which supposedly had been checked, had managed to poison the river, Ms Gray concluded the story. It appeared that, unknown to the scientist who tested the waste in the holding tank, the factory had changed its production. The scientist had assumed the waste would be safe, as it had been the previous weeks, and had failed to test it, rushing off to meet friends for a birthday celebration.
She was fined pound;10,000 but had learned her lesson and never did it again.
Initially a science technician in a secondary school, it is 15 years since Ms Gray put her dream of being a freelance science tutor in primary schools into practice. She began preparing her 14 teaching stories and producing kits, guides and worksheets for P1-P7 pupils. Then, as the "Science Sleuth", she began travelling across Scotland visiting schools and science fairs.
"Science has for too long been taught in a boring way," she says. "I like to make science interesting and informative to children through stories.
There should be a point to doing science, that's why I get children to solve problems."
Although she prefers to work in the Lothians and Edinburgh, where she lives, twice a year she visits Dundee, where schools are invited to visit her workshops, and she has attended Aberdeen's Techfest of science, technology, engineering and mathematics every autumn since it began 11 years ago.
Most primary teachers would welcome any assistance going with this daunting subject and an important part of Ms Gray's work is to educate teachers to carry on what she has begun. Last month she visited Fife to give a demonstration for teachers and in December she is providing an in-service workshop for teachers, through the Institute for Science Education, in Edinburgh.
Science does not have to be frightening, and after witnessing one of Ms Gray's lessons, many reluctant teachers would be prepared to give it a go.
Anne Gray, email@example.com