After Doreen finished speaking with her son, Erik couldn't stop himself from smiling a bit at the sight of a lovely mother-son moment. He empathised with her. He took back the holo-pad and ended the call by telling Peter "You know, if you get bored, you can always activate the ball-field outside... Anyway, I'll be home soon." A typical suggestion along the lines of "go play outside, move around, don't sit inside all day. He himself sniffed, amused at the thought.
"Those two. They play like they've been friends forever."
A smirk from Erik "Much like my brother and I, back in the day... You know, it's really nice to see Peter having someone he enjoys spending time with."
Both Doreen and Erik then returned to the lab. In the minutes they've been away, another portion of Frederick's had been reformed by the nanites, up to the wrist. "Shouldn't be long now... Ten minutes at most." Valders added. "Sounds good." Erik nodded, content that the crisis had been averted and their project was about to prove amazingly useful.
Eventually, the nanites finished the job, the patient now having his entire left arm back in place as if it had never been missing. Erik and Valders checked their respective equipment, ensuring that everything was alright and the nanites entered the desintegration phase. Being based on zinc, they would quickly self-destruct, leaving only inert molecular materials behind, that would eventually be absorbed by the body and used as resources.
Everyone was relieved, but the two scientists didn't start cheering just yet. After he checked the final numbers, Erik commented "It's not over yet. While there's no risk of rejection, considering the new arm is made entirely from his DNA, there's still a chance something might have gone wrong in its internal structure. Plus, right now the arm is being filled by fluids, blood... and the brain is probably accommodating with the new neurological input."
He turned to Doreen and the medical crew as a whole "Our part is done here. He should be moved to someplace more comfortable and you need to observe his progress. Please let us know the moment he wakes up and what the results are." It was clearly time for them to start packing up the equipment, since the operation was over and... hopefully... a complete success.