When Tabitha Smith's mutant nature manifested at age 13, she ran away from her abusive home. After an encounter with the otherdimensional Beyonder, Smith was recruited into the Vanisher's band of thieves the Fallen Angels. Briefly taken in by the X-Factor group as a trainee, Smith soon returned to the Fallen Angels only to rejoin her former fellow trainees as the X-Terminators. Subsequently joining the New Mutants, Smith stayed with the team after they were restructured by Cable into X-Force. She began a relationship with Cannonball that would last until he graduated and joined the X-Men.
Following her father's near-death experience with Sebastian Shaw and Holocaust, Tabitha underwent a drastic change in looks and personality. She renamed herself Meltdown and became something of a loose cannon. When ex-spy Pete Wisdom assumed leadership of X-Force, he introduced them to the shadowy world of covert operations. After a mission, the team was considered deceased (including Tabitha).
When Cable reformed X-Force, Tabitha briefly rejoined the team. Later, she resurfaced as a member of Nextwave. She later appeared as a captive of a resurrected Leper Queen as a part of sentinel-from-the-future Bastion's plan to wreak havoc on the remaining mutant populace. However, she was rescued by members of the new X-Force and taken to San Francisco to be with the X-Men.