Well, without having read the 'the big island crime novel' in detail, we can assume that there is likely a protagonist who is on a journey to solve the crimes on the big island. This could be a private investigator or a local law enforcement official. There would also be antagonists, the criminals causing trouble on the island. And there might be some side characters like witnesses, informants, or people who are indirectly affected by the crimes, such as local business owners who are losing customers due to the high crime rate.
One main theme could be the exploration of justice. In crime novels, the pursuit of justice is often central. Another might be the dark side of the big island itself, like its seedy underbelly. And perhaps the theme of redemption for some of the characters involved in the crimes.
Philip Marlowe is one of the main characters. He is a private detective with a sharp mind and a sense of integrity in a rather corrupt world.
In 'The Big Sleep' crime fiction, the most prominent character is Philip Marlowe. He is a private eye with a unique personality. Carmen Sternwood is a complex character whose actions are part of the mystery. General Sternwood, Carmen's father, is also important as his request sets the whole story in motion. There are other characters like Eddie Mars who add to the complexity of the plot.
There might be a castaway who has to adapt to the island life. There could also be a group of sailors who end up on the island by accident. Among them, there may be a leader figure who tries to keep everyone in order and find a way to get off the island. Additionally, there could be a local on the island who helps or hinders the outsiders depending on the story's direction.
In a 'holy island crime novel', the sense of isolation of the island is often a key characteristic. This can make it difficult for the characters to get help or for the police to arrive quickly. The religious history of the holy island can add an extra layer of mystery. For example, there could be ancient superstitions or religious legends that are intertwined with the crime. The local community on the island, which is often small and tight - knit, can also play an important role. Their secrets and relationships can be at the heart of the mystery. Moreover, the natural landscape of the island such as cliffs, beaches, and forests can be used as settings for different parts of the crime, from the crime scene to places where evidence is hidden.
Without having read 'The Island' by Benchley, it's difficult to name the exact main characters. But it's common in novels set on islands to have a protagonist who is a bit of an outsider. Maybe someone who has come to the island to escape their past or in search of something. There could also be a character who is native to the island and acts as a guide or a source of knowledge about the island's secrets.
There could be immigration officers or officials at Ellis Island as main characters too. They might play a role in determining the fates of the immigrants, and the novel could explore their perspectives, like how they deal with the flood of new arrivals and the rules they have to enforce.
There could be a group of friends who decide to visit the island together. One of them might be the leader type, always making decisions. Another could be the comic relief, always cracking jokes even in difficult situations. And perhaps there's a more mysterious character whose past is somehow related to the island.
There could be a variety of characters. There might be a strong and resourceful man who is good at building shelters and finding food. There could also be a woman with a kind heart who takes care of the others emotionally, and perhaps a child who brings out the protective side of the other characters.
I'm not sure as I haven't read it. But usually in a novel, the main characters could be locals from the island, or outsiders who come to the island and get involved in the story in some significant way.