Dr. Ernst Robinson, a medical professional and patriarch, relocates his family from Bern, Switzerland, to Australia upon his friend Dr. Elliot's request for help during a doctor shortage. This decision sparks their voyage. During the journey, he provides crucial medical aid to a pregnant woman just before a severe storm hits.

Following the shipwreck, Robinson leads the family's survival efforts on the uninhabited island. He actively explores, performs carpentry, builds shelter, and collaborates closely with his eldest son Franz. His medical skills prove vital, treating injuries like those of the castaway Mr. Morton using salvaged antiseptics.

Robinson maintains a consistently calm and stoic demeanor throughout their ordeal, even during volcanic tremors revealing the island's instability. He arranges respectful burials for the deceased, including the ship's captain and a previous castaway, Eric Bates. When Morton proposes building an escape vessel due to the volcanic threat, Robinson supports the plan and coordinates the family's boat-building efforts. After over a year on the island, he leads their successful voyage to Australia, where the family travels by train to Melbourne and reunites with Dr. Elliot.

His interactions reflect principle: he initially distrusts Morton after witnessing coarse behavior but later acknowledges Morton's underlying good intentions upon reviewing evidence of his rescue attempts. Robinson also oversees the children's education during the island stay, teaching the Aboriginal Australian boy TomTom basic literacy and mathematics.