Constellation’s intriguing Incognito, Gerrad Alex Taylor deftly inhabits just one memorable character in Christian St. Croix’s moving Monsters of the American Cinema (★★★★☆), a Prologue Theatre production at the Atlas Performing Arts Center.By the look and sound of this evocative, regional premiere, staged by Prologue artistic director Jason Tamborini, the playwright put that character firmly on the page.