It wasn't over. Even though they were forced into quarantine there was still so much to do to continue to avoid a catastrophic event. The lack of Intel on the extent of the damage exasperated the situation.
It was very rare Walter called for backup in a situation but even the almighty leader had his limits- he could beat a lot of things but the risk of radiation poisoning when they were that close to the center was too high- he knew they needed time to decontaminate while he formulated another plan. Unfortunately the plan he had required them to stay in the country longer liaising and guiding the team he'd called upon.
Happy was in her element coming up with new tools and machines to support the temporary extension to the team from Bosnia (where she, Sly, cabe and toby were currently on assignment) and Slyvester was happy to help run through the probabilities when he had a moment but they couldn't help him in physicality from there. He couldn't demand they stop what they were doing and travel to Japan either- their work was vital in a different way.
All this extra time away though led to the question- what to do with Ralph? His babysitter didn't do long term, Drew was (as normal) no where to be found and there was no way he was putting him in temporary Foster care after seeing how the system had affected Happy.
It took a while for the light bulb moment to hit him, but when it did he couldn't decide whether it was a good or terrible idea...
His parents.