Lost Child follows an army veteran, Fern (Leven Rambin), who returns home in order to look for her brother, only to discover an abandoned boy lurking in the woods behind her childhood home. After taking in the boy, she searches for clues to his identity, and discovers the local folklore about a malevolent, life-draining spirit that comes in the form of a child; the Tatterdemalion. Is this boy truly a lost child, or something more nefarious?