The Believers (1987)

After the death of his wife, police psychiatrist Cal Jamison moves to New York. There he has to help in the investigation of the murder of two youths, who seem to have been immolated during a cult ritual. Jamison believes it's been Voodoo and, ignoring the warnings of his housekeeper, enters the scenery and soon gets under their influence. They try to get him to sacrifice his own son.

The Believers is a horror movie featuring Martin Sheen.

The Believers is currently streaming for free (ad-supported) on The Roku Channel and Tubi TV and it's also available on Amazon Prime Video.

It is also possible to buy The Believers on Vudu.