The House of Hades
Leo falls onto Calypso's island, breaking her dining table in the process. Unlike all other heroes who came to Ogygia, Calypso does not fall in love with Leo immediately, nor Leo to her. In fact, she is thoroughly disgruntled by him, shouting at the gods about why they would send her someone like him. Leo, miffed about being referred to in such a way, gives her the sarcastic nickname "Sunshine". However, throughout Leo's time on the island, he starts to fall in love with her; Calypso starts to feel the same way, and begins acting nicer and not closing him out.
While this is happening, the war against Gaea rages on. Leo is desperate to know how his friends are getting along, so he builds a device to see other places, but it doesn't work. Calypso tells him a magical incantation could help, and despite his initial doubt, it works. The device shows the Romans marching toward Camp Half-Blood and Leo's friends. In one of the last scenes, Reyna shows up, but then the scene cuts out. Leo smacks it, wanting to see more, and Calypso asks him whether Reyna is his girlfriend. He denies this, confused on why she would even wonder that.
Leo bangs on the device, shouting that he "needs" to see more. Suddenly, Gaea appears and mocks him for saying "need." Gaea offers Calypso her freedom if she kills Leo. However, this enrages Calypso, and she insists that Ogygia is her home, while Gaea is the intruder. Leo is stunned that she would turn down the deal, but Calypso brushes it off, saying they need to get back to work.
When they are building the boat to get Leo off the island, a raft comes. This particular raft only appears when Calypso falls in love. Before Leo goes, Calypso kisses him, and he swears to come back to her. "I'm coming back, Calypso. I swear it on the River Styx."
The Blood of Olympus
Leo dies and then comes back to life with the Physician's Cure. He returns for Calypso on his dragon Festus. Thus, he fulfills the third line of the Prophecy of Seven: "An oath to keep with a final breath". The oath was Leo's promise on the River Styx to return to her, making him the first man to ever visit Ogygia twice. She hugs him and they "ride off into the unknown".
The Hidden Oracle
Leo comes back with Calypso, and they are enlisted to help Apollo on his quest. Then, in the next book, Leo and Calypso go to Indiana with Apollo and go to the Waystation house. Leo must go to Camp Jupiter, but once again promises to return and go to high school with her.
This ship is relatively popular within the fandom. However, there are not many fan fiction centered around it, as it is usually a background ship.
- Calypso is the first out of four love interests to genuinely have any real romantic interest in Leo.
- Leo is the only man who has ever reciprocated Calypso's affections and actually wanted a relationship with her.
- Caleo means "Flame" in Latin.