|“||Don't be too discouraged when you read it, dear. He does have your interests at heart.||”|
Martha is a snake caught by the god Hermes. She is immortal, though she isn't a monster. Demigods and gods can hear her speaking to them in their minds. Martha is always seen with her male counterpart and husband George.
Martha makes her first appearance when Hermes visits Percy near the lake in Camp Half-Blood. She gives the Thermos of winds as a gift for Percy, as well as continually having to scold George for saying things that are out of the conversation or for teasing Percy.
Martha appears the second time with Hermes to deliver a letter from Percy's father, Poseidon. She advised Percy to not be discouraged when he reads it.
Hermes arrives in Olympus to deliver a message, Martha and George with him. Percy says something that anger Hermes and when he tries to punish him, Martha and George come to the rescue and whisper to Hermes that Percy has the curse of Achilles.
George and Martha are stolen by Cacus when Hermes accidentally leaves them in the Hermes Express truck. Cacus tried to make the snakes obey him, but Martha calls out to Percy when he comes to save them with Annabeth Chase. While Cacus again attempted to make the snakes follow his command, George and Martha would try their best to mess him up, such as when they changed into a phone when he tried to turn Annabeth into stone. Despite their best efforts, Cacus eventually got Martha and George to change into Laser Mode, and he chased the two demigods around New York. When Percy got the caduceus back, George and Martha gladly changed into Laser Mode to defeat Cacus.
Martha is much more firmer, kinder and more understanding than her counterpart George. While he normally asks for rats or guinea pigs, she is constantly getting trying to get him back on topic and correcting him when he makes a mistake. Whenever Percy is confused, she would encourage him and guide him back.
When the caduceus morphs into a phone, Martha is on the antenna. She becomes a pen when their costumers receive their packages to sign their receipt.
- Martha and George danced the Macarena at their wedding.
- Martha appears as a blue snake in the film adaptation, Percy Jackson: Sea of Monsters.