After Rex was mysteriously sent into the future, he found some changes overwhelming; one of them being the fact that Agent Six and Doctor Holiday were missing. It was revealed to him by Black Knight that after Rex's disappearance in the past, they split ways with Providence. Eventually, they found one another and Rex teamed up with them. Holiday, Agent Six, Bobo, and White Knight who had a different base and were affiliated underneath Providence's radar.
They helped put a stop against the Consortium and Black Knight, and eventually became restored with Providence.
Back in Black
When Rex tried to escape Black Knight, Rex was knocked out by two anonymous agents with pilot helmets on, later to be revealed Holiday and Six. Holiday, who was relieved to have Rex back, greeted him graciously with a hug. It was revealed that they both, along with Bobo and White Knight, had built a base of their very own.
Crash and Burn
Things had changed for Doctor Holiday since things had changed. She worried over Bobo Haha and his late night hangouts and Rex's well being. Holiday insisted that Rex was fine but found it hard to resist checking on him anyway.
After Rex encountered an underground motorcycling race group, one of them had crashed and was knocked unconscious. Immediately, he was taken to Holiday for an examination. When studying him, Holiday revealed that he was pumped full of some sort of altered nanites that were killing him. Holiday was out of loss, not knowing how to help him.
Later, Rex went out with the same group and encountered the same situation with Rand. Again, Rex called Holiday. Eventually, the racing group revealed getting nanite prototypes from Valve. After Valve is defeated, Holiday detoxifies the two young men who Rex both brought in, allowing them to be reunited with their friends. Holiday and Six suggested taking the prototypes, saying they could be useful at their new base.
Riddle of the Sphinx
Doctor Holiday was exploring the pyramids of Egypt with a Pyramid guide. She had accidentally set off a booby trap, allowing something to "awaken" in the tombs.
Missing for a few days, the group headed out to search for her. Rex, Six, and Bobo expected Black Knight to have something to do with it. When she confessed that she didn't have a clue on Holiday's whereabouts, they went on their own.
Soon they bumped into her in the pyramids and encountered Gharun Set, a dead pharaoh powered by nanites. While Rex chased him, Holiday was cornered by undead dogs powered by nanites. The group, including Black Knight, fought them off until they had mysteriously fell to dust. In the Great Hall of the tombs, Holiday was even more fascinated by all of the ancient works that were yet advanced. Hoping to come back another time to examine the works, Black Knight destroyed the evidence, leaving Holiday with much grief.
When a strange pollen released from an EVO plant goes around turning others into pollen spreading EVOs, Holiday quickly warned Rex that he must stop it before it's pollen goes worldwide which could be in a matter of hours. Holiday supported the group by travelling elsewhere to do her own work, but was cornered by vines. She fought her way free with the aid of Black Knight and the group had succeeded.
Guy vs. Guy
After some of Doctor Holiday's equipment went missing for a prank that Bobo wanted to play on Noah, she called Rex to make sure if he had seen Bobo after she witnessed him snooping around the lab earlier. She told him that the magnetic containment pod she had was now missing. She stated that it held some rare radioactive material and that it could be dangerous if it's exposed to oxygen. Frightened by this, Rex lied and tried to stop it on his own with Bobo. Seeking help from Noah, he played back a remarkable prank with the help of Holiday, who told Noah how to rewire the pod just in the nick of time, allowing their plan to backfire. 
Black and White
Doctor Holiday helped the group infiltrate the new Providence. Holiday's main objective was to break into Providence's mainframe. With the use of Agent Six's magna blades, she used them to redirect and absorb all the mainframe's electric currents, that produced an electric field, in order to safely travel inside. From inside the mainframe she kept a close eye in all of Providence's security cameras. Unfortunately, she had gotten cornered by Providence agents and an EVO dog. Just in time, Six came in to save her. Later, she safely escaped with him. 
Doctor Holiday was communicated by Rex and Noah and was notified that they had found an EVO named Feakins. Feakins, who was strongly wanted by Providence, was on the run with Noah and Rex and were under disguise. Once Holiday was told of his powers, she told them that Black Knight only wanted him to make Providence's job much easier, which was capturing EVOs. For Rex's sake, she planned a rendezvous. Meeting at the first rendezvous, it was heavily patrolled by Providence agents. Holiday planned to meet elsewhere and eventually meeting up with one another. Unfortunately, they were cornered by Providence. Using a stealth technique with the Mobile command center, Holiday managed to escape the pursuit. She stationed Feakins in an ice cream truck to be hidden away from Providence.
As a distress signal came in from Manhattan, the team rushed to the scene. Holiday supported the group to tell them of the space time rift they had encountered. When the group encountered the strange anomaly, Holiday told Rex she has not a clue what was happening. However, she warned Rex of two unidentified beings come out of a space time rift, being Ben Tennyson and Alpha.
After Rex battled one of the mysterious invaders, Holiday backed up Six after he fought Alpha. When she had gotten her hands on a sample of the creature's remains, Holiday inspected it, but implied that it's something she'd never seen before—inorganic and made up of chemical compounds she'd never known of. Caesar came in to take the sample to do more tests himself.
After Six goes comatose after a battle, Holiday worried and began to interrogate Ben Tennyson after capturing him, but he eventually escaped. Shortly afterward, he makes amends with Rex. Holiday then notifies Rex, via communicator, that Alpha had returned to their base. As Alpha broke in, Holiday faced him. Telling her that she is no use for him because of dormant nanites, he demanded for Rex instead. Angered, she attacked him with a laser firearm. Having no effect, he grabbed her and squeezed her nearly to death, but she is saved by Rex and Ben. A battle occurs where Rex is almost drained by him, but Holiday aided him by firing her weapon to break them apart. Being outnumbered, Alpha fled.
When Six was out of his coma, Rex mentioned that he would like to see Ben once again. Holiday stated that with there being so many dimensions, the chances of them meeting are very little. Shockingly, to Holiday, Caesar entered their base, and gave Rex back his Omega-1 Nanite after it was taken by Alpha. Leaving the group satisfied. 
A Brief History of Time
When Rex and Bobo went to investigate the ruins of the Hall in Cairo, Egypt, Holiday monitored them of their every move. Throughout the investigation, Holiday was led to believe that Van Kleiss had built a time machine to travel through time.
When Doctor Holiday was awoken from her sleep due to an alert in the situation room, unaware of John Scarecrow disguising himself as her earlier, she was confused to Rex's comment when he questioned her on how quick she changed.
Later, Holiday was tricked into being kissed by John Scarecrow who masked himself as Agent Six. Running into the real Six, she thanked him. This confused Six, therefore angering her. Eventually, John Scarecrow was revealed and the team tracked him down. At the brink of Rex's demise, Holiday came in to easily defeat him, more upset over what he did to her.
In the beginning, Doctor Holiday made a brief appearance monitoring Rex as he communicated with the Nanite World. Waking up from a bad communication, she told him it wouldn't be easy. She listened to Rex as he told her something bad, involving the Nanite World, is about to happen. 
When a prison break caused Gatlocke, Valve, NoFace, and Hunter Cain to escape, it allowed Rex to have an overload. Holiday demanded that Rex came back to the base to have them offloaded. After putting Rex into the chamber, she spotted the escaped prisoners on surveillance cameras. She engaged traps to hold them back and faced them on her own to create a diversion. Hunter Cain managed to find out that she was stalling and entrapped her by causing a blockade.
Eventually when Rex defeated them, Holiday revealed that the breakout was planned to keep Rex busy and it permitted Black Knight to get her hands on another Meta-Nanite.
Rock My World
In this episode, much of Holiday's motherly side is shown. Throughout the episode, Holiday constantly called both Rex and Beverly, telling them to wear earplugs, to drink only bottled water and when she was going to pick them up from the Trendbenders concert.
Later, Holiday took Beverly home after reluctantly leaving Rex to guard the Trendbenders and highly refusing Beverly join him.
It started off with Black Knight ambushing The Plant and Holiday fought back along with Bobo. After Rex was taken by Black Knight, Black Knight ordered for her pawns to kill Holiday along with Bobo and Six.
To her dismay, Holiday and the group survived. Holiday began to panic and wanted to save Rex instantly. Once Agent Six told her that they needed an army to fight back, she mentioned that Agent Six was a man who did the impossible. Just in time, the group got backup from Providence.
Later, they attacked the Consortium who was battling Rex to the point where he almost died. Running in to rescue him, Holiday and Six carried him back for recovery.
When Rex fully recovered and decided to have a rematch with the Consoritum, he lost miserably, bringing Holiday and Six to his aid once again. Waking up, the group infiltrated the Consortium base to stop them from using the Meta-nanites once again. Once Rex gained all the meta-nanites and gained godhood abilities, Holiday watched in astonishment.