The Neanderthal Man

A bar waitress who becomes entangled in Groves's experiments and the ensuing danger. She exhibits resilience and vulnerability as the Neanderthal threat closes in and personal loyalties are tested.

A brilliant but obsessive scientist who injects himself with a serum that regresses him toward Neanderthal traits. His arrogance drives the plot and leads to a chilling, tragic downfall.

A researcher who studies Groves's work, gathers evidence, and attempts to stop the regression nightmare. He confronts danger in the field and strives to rescue those harmed by the serum.

Groves's fiancée who travels with the investigation and is drawn into the terror as the Neanderthal Man closes in. She represents vulnerability amid scientific turmoil.

Groves's daughter who aids the investigation and helps connect Harkness with the case. She provides a humane perspective against her father's hubris.

A townsman who photographs Nola and is killed by the Neanderthal Man, underscoring the real danger of Groves's experiments.

A hunter who is killed by Groves during one of his transformations, illustrating the broad reach of the serum's threat.

The bar owner who witnesses the fallout and serves as a local anchor amid escalating danger.

The local physician called to treat the injuries and help untangle the mystery of the transformation.

Groves's deaf-mute maid who is regressed by the serum, highlighting the ethical stakes of the experiments.

A local naturalist who mocks Groves's theory but becomes involved as the mystery deepens.

A townsman who notices the strange occurrences and serves as a link between the community and the unfolding scientific drama.