Scientists from the mid-nineteenth century have searched for the fossil remains of the "missing link" in evolution - the half-man, half-ape that would explain where mankind came from. But over the last century and a half, it has been the idea of what a missing link is that has evolved. The history of this scientific quest - peopled with fanatics, frauds, amateurs, professionals, the lucky, the unlucky, the unfairly neglected and the undeservedly praised - is the subject of this documentary. Reenactments depict scientists making their discoveries and then stretch back hundreds of thousands, even millions, of years to depict the typical lives of our human and human-like ancestors. Interviews with leading scientists fill in the details.