In a steampunk fantasy world, guilt-ridden inventor Al is faced with a devastating reality when his infant granddaughter falls gravely ill with a mysterious illness. Determined to save her, Al embarks on a treacherous quest to retrieve the only known cure from Neanderthal Island, accompanied by his timid son, Tom, and fragile grandson, Sam. As they navigate the challenges of the fantastical world, confront personal struggles, and forge a bond, they encounter savage inhabitants and must rely on their unity and courage to overcome dangers. Through shared experiences and sacrifices, the family discovers their strength and resilience, ultimately triumphing over the forces opposing them to obtain the cure and save their loved one's life. However, their actions inadvertently trigger revenge in the heart of the Gehennian king, leaving a poignant conclusion to the story.

In a guilt-ridden inventor's quest to save his gravely ill granddaughter, he joins forces with his timid son and fragile grandson on a treacherous journey to Neanderthal Island, facing savage inhabitants and ancient secrets to obtain a rare cure before time runs out.