In 1715, Rhona's bureau in Havana was sold out to the Templars by the traitorous Assassin Duncan Walpole, to which Edward Kenway, on delivering documents to the Templars for Walpole's reward, inadvertently endangered Rhona's bureau. To make penance, Edward arrived two years later, to assist Rhona as she was being besieged by Spanish troops.
After fending off the attack, Kenway requested Rhona's assistance in locating the Templar key required to access a set of robes at his base in Great Inagua. Rhona asked him how he would respond if she were to take the robes for herself, to which Kenway pointed out that they would not fit her. Reluctantly, she agreed to help him in exchange for defeating the Templars in Havana, although she had been wounded by the troops during the fight and couldn't conduct a proper investigation on her own.
Edward searched Havana's marketplace for clues, finding a pickpocket running from a group of Spanish troops. After killing both the thief and the soldiers, Kenway looted the man's body, finding a letter revealing that the pickpocket, along with several other thieves, had been funding the Templar commander Hilary Flint and his attempts to eliminate the Havana Assassins through an arms race.
By this point, Flint had accumulated a large stock of gunpowder, which he kept stored throughout the city. To eliminate Hilary's advantage, Kenway located and destroyed four gunpowder kegs, depleting the Templar's stores. This final act brought Flint out into the open, and he went to the docks to move the rest of his powder offshore.
Rhona and Edward devised a final plan, where she would distract Hilary while Edward moved in for the kill. In his final words, Flint regretted that he and Rhona hadn't had the chance to fight on the same side.
By 1721, Edward revisited Rhona while on the hunt for Grand Master Laureano de Torres y Ayala, while Havana was placed on high alert. Edward showed Rhona the Crystal Skull from the Observatory and inserted Torres' blood vial into it, showing his location. Subsequently, while he tracked down Torres, Edward gave the Skull to Rhona for protection.
Edward later returned to her bureau, revealing that the man he assassinated was a decoy, and instructed Rhona to warn Ah Tabai that Torres was headed for the Observatory. Rhona returned the Skull to Edward, and the captain headed after his target.