Albinism is a non-contagious, genetically inherited disorder, affecting about 1 in 20,000 men and women around the world, regardless of ethnicity and geographical location. Sufferers are afflicted by a congenital absence of melanin, a pigmentation defect in the hair, skin and eyes that causes vulnerability to sun exposure and bright light. Many have very poor vision as a consequence and in tropical countries especially they can be vulnerable to skin cancers if unprotected from the sun.

What albinism is absolutely not, is an indication that the afflicted person is any way invested with magical powers.

Though it might seem absurdly obvious, the point is worth stating so starkly because in parts of sub-Saharan Africa especially, albinos have traditionally faced discrimination and prejudice - innocent victims of a still widespread belief that the condition is in some way associated with the supernatural. To some, a white-skinned African person is seen as a kind of phantom or ghost, who rather than die will dissolve or disappear with the wind and rain. As a result, in some communities, albinos have been feared, shunned and socially marginalised.

Over the last five years in Tanzania, however, the situation has become much, much worse, with albinos increasingly subjected to murder and mutilation because of a completely spurious myth that albino body parts are effective in witchcraft rituals. Despite international outrage and repeated attempts by the Tanzanian government to stamp out this truly appalling practice, since it first came to light many albinos have been hunted down and attacked purely for their limbs and organs. Indeed the incidents seem to be increasing. Since 2008, at least 62 albinos have been killed in Tanzania, 16 have been violently assaulted and had their limbs amputated and the bodies of 12 albinos have been exhumed from graves and dismembered.

Against this background, it is perhaps not surprising that estimates of the numbers of albinos in Tanzania vary significantly. Officially there are around 5,000 registered, but the country’s Albino Association says the real number is in excess of 150,000. They say that many albinos are still kept hidden by their families because of the stigma some associate with the condition or because of fear that they might be attacked.

In this remarkable episode of Africa Investigates, Tanzanian journalist Richard Mgamba, albino community representative Isaack Timothy and Ghanaian investigative journalist Anas Aremeyaw Anas set out to discover what lies behind these sickening attacks and to uncover and confront some of those behind the grotesque trade in body parts for witchcraft rituals.

In the process they meet two albino children, victims of vicious assaults that occurred in the weeks the film was being made. One of them is a 12-year-old boy who had part of his hand cut off, allegedly with the connivance of his father who is now in police custody and awaiting trial. The other is a 16-year-old girl whose left arm was hacked off by a stranger with a machete.

But Anas, who goes undercover in the guise of a businessman seeking to get rich, also comes face to face with a witchdoctor who tries to sell him a potion containing ground up albino body parts. Not surprisingly, when the offer is made, Anas makes his abhorrence very plain.

Right from the start of this film, viewers may find some of the images disturbing.