Shadow Jones (also separately named by her birth father's family as Maria Isabella Puzorelli) is the adopted daughter of Casey Jones and April O'Neil and an adopted niece and friend of the Turtles as well as the adopted granddaughter of Splinter.
Additional details for Shadow's story were written for the Image continuity. Like the rest of the Image continuity, it was expanded from existing Mirage continuity of volumes 1 and 2, but these details were disregarded by future Mirage canon of volume 4 and Tales of the TMNT volume 2.
Soon, however, Shadow encountered ghosts from her past: Her biological father was Albert Puzorelli, a mafioso who had died shortly after he had left her mother. His father, Antoine Puzorelli, learned of Shadows existence and hired the Foot Clan to abduct her for him.
One night when being baby-sat by Michaelangelo, Shadow heard a knock on the door and answered it. Captured by the Foot Clan, she was taken to her paternal grandfather, Antoine Puzorelli. When Raphael learned of Shadow’s abduction he sough council with the Foot Clan, confirming their involvement. He then agreed to kill Antoine Puzorelli for them in exchange for Shadow, a mission he couldn’t complete. Michaelangelo stepped in, disguising himself as a priest in the cathedral where Shadow was to be baptized by Antoine under his family name. Only moments after being baptized (making Antoine her godfather), Michaelangelo dropped his disguise and rescued her, taking her to the top of the cathedral and using his shell to make himself appear as part of the gargoyles statues. Shadow was then returned to Casey and April (TMNT Vol. 3, #6 - 8).
Antoine Puzorelli then had his thugs put his apartment on surveillance in an attempt to locate Shadow. When April caught on to this and told Casey, Casey, April, and Shadow went into hiding in the Turtles’ current hideout in the mausoleum of Westwood Cemetery. While Shadow watched, Casey accidentally clubbed Raphael when he returned to the hideout, thinking him an intruder. Shadow, Casey, and April met back up with Leonardo and Michaelangelo when they brought Donatello to their mausoleum hideout, where he was then revived (TMNT Vol. 3, #11, 12 & 15). When Leonardo chooses to give up his artificial, removable hand, Shadow asks if she can keep it. Leonardo gives her permission (TMNT Vol. 3, #23).