In the 1960s restoration began on Newgrange, an ancient passage grave in the Boyne Valley in Ireland. During the restoration of Newgrange, a strange phenomenon was revealed. On the winter solstice, the passage of this mound aligned with the rising sun through a specially constructed aperture, the roof box. The consensus initially was that the builders of these monuments, Neolithic farmers, were a primitive agricultural people and that these passage tombs were constructed as burial places.

Martin Brennan is a specialist in prehistoric art and writing. After spending three years studying prehistoric art in Mexico and a similar period in Japan he moved to Ireland to study the stone carvings at the Boyne Valley complex. Brennan noticed the re-occurrence of certain patterns across several sites. He established that the art carved into the kerbstones and walls of the passages were directly related to the function of the mounds. That function, he discovered, was not as a grave as previously considered by archaeologists, but that the mounds were in fact astronomical observatories built with an underlying symmetry and geometry. Brennan's research revealed that Newgrange was not the only astronomically aligned mound. Newgrange is the most recently built and impressive of the monuments in Ireland and at 3,200 BC it pre-dates Egypt's first pyramid by 600 years and Britain's Stonehenge by 1000 years. Knowth and Dowth in the Boyne Valley and the Louh Crew mounds were also found to align to the rising and setting of the sun at critical times of the year: solstice, crossover, quarter day and equinox. More remarkably on these critical dates, the beam of light illuminates, one after another, images carved into the stones - the solar and lunar symbols, calendars and sundials.

Martin Brennan began to systematically decipher the symbols. He uncovered an ancient writing system that dealt with tracking the solar and lunar cycles over scores of years. Sundials and lunar calendars are seen to exist here earlier than anywhere else in the world. The calendar stone on Knowth shows the 19-year lunar cycle, the Metonic cycle. This cycle is not supposed to be discovered until the 5th Century BC in Greece.

Brennan's findings point to the fact that the builders of the Boyne Valley monuments had studied and recorded the movements of the stars for centuries. They had taken the first intellectual steps to understanding their surroundings and had created a science. In the process, they made discoveries that were not supposed to happen for centuries and in some cases thousands of years. This documentary will reveal hard evidence that will forever change our perceptions of this period in mankind's history. In a detective story played out on the western European landscape, we reach back into our distant past to reveal for the first time The Secrets of the Stones