A/N: Über-brownie points to whoever spots the (admittedly obscure) reference to 3rd-Doctor-era Classic Who arc in this chapter! (Warning: if you haven't seen the arc in question, there's probably little or no chance you'd catch it...) Hint: it backs up the plot. Also, much technobabble! Yay!

"What sort of news?" asked Maria quickly. Mr. Smith didn't often give warnings...

"Luke's condition was difficult to analyze," said the computer. "His results did not fit any normal pattern. It was difficult to even ascertain his species."

"My watch was having the same problem," said Sarah Jane. "But why? What's causing it?"

"I believe that Luke's genetic structure is deteriorating," said Mr. Smith simply.

There was a beat of silence, then both Sarah Jane and Maria said, "What?" at the same time.

"What does that mean?" asked Maria.

"Never mind that, what's causing it?" Sarah Jane cut her off.

"It means," said Mr. Smith calmly, "that Luke's genetic code has been rendered unstable. The overflow of raw telepathic energy has broken the lock on his helical stability. Luke was already especially susceptible to fluctuations of this kind, and the flow of energy from the activity of telekinesis caused the lock to break entirely, causing random genetic decay and the gradual release of a special type of bioelectric energy."

Maria still looked confused. "What...?"

"Luke's genetic code is decaying," said Sarah Jane, still staring wide-eyed at Mr. Smith. "I think the Doctor might have mentioned something similar happening once - "

"Yes, Sarah Jane," said Mr. Smith matter-of-factly. "However, that was a case of genetic deconstruction aimed at de-evolution. Here, the degeneration is much more gradual, but it is completely random."

"So it's not changing into anything..." Sarah Jane said, her voice tight with trepidation.

"What is going on?" asked Maria shrilly.

"It's difficult to explain," said Sarah Jane distractedly. "It basically means that the code that keeps Luke's body in order is randomly changing."

"You mean pairs in his DNA sequence are just swapping out," Maria tried.

"Or disappearing entirely," Sarah Jane confirmed. "How did you - "

"We did a unit on genetic theory a few months ago. But aren't genetic changes what cause cancer?"

"Basically, yes," Sarah Jane admitted. "But for Luke the changes are much more rapid. His cells are degenerating from the inside out. Cancer's the least of our problems." She turned back to Mr. Smith. "But there has to be a way to reverse the damage?"

"As it was altered thousands of times by the Bane, Luke's DNA is particularly vulnerable to decay, but this also makes it more easy to reprogram. I can in theory send out an energy pulse reverting the coding to its proper state."

"That sounds like a simple fix," said Sarah Jane. "But what do you mean, 'in theory'?"

"Unfortunately, this method requires a complete transcription of Luke's original genetic code."

"You just took one," said Maria desperately.

"That scan was taken after the degeneration had begun," said Mr. Smith. "It is not a complete or error-free transcript, and as such is unsuitable for such a purpose."

"But you scanned Luke before!" said Maria. "When you were testing Luke's identity against Ashley's. Can't you use that data?"

Mr. Smith whirred for a few seconds, seeming to be trying to process Maria's question. Finally he answered tentatively, "I cannot find any record of such a scan."

"What?" said Maria, annoyed. "But - "

"At what time was this scan taken?" asked Mr. Smith.

"Sarah Jane hurried forward, tapping at the keyboard, and then recited a long string of numbers and commands that Maria guessed specified the date, her exact instructions, and other details.

Mr. Smith buzzed again. "No record of this type exists in my memory." He continued before Sarah Jane could protest. "Last comprehensive backup was several days before the scan. The data was likely lost in the crash."

"Well, is there any way to bring it back?" Sarah Jane cried.

"I'm not sure. It's possible that the data cannot be retrieved at all in the current state of my records."

Sarah Jane and Maria stared at the computer in consternation for a few moments. Then Sarah Jane nodded to herself.

"All right then. Maria, come with me. We need to talk to your father. Wait there, Mr. Smith." She swung open the attic door.

"What is Dad going to do?" asked Maria, confused.

"See if that Armageddon virus is reversible," said Sarah Jane as they hurried down the stairs.

"But - "

"Look, we have to fix this as soon as possible in case something else happens. We'll worry about later later. Come on!" And they hurried down the stairs and out the door.

***

A few moments later, someone else entered the attic. "Mr. Smith, you're about to receive orders that will directly countermand your purpose to protect this planet from hostile intent."

The computer didn't seem surprised to see the newcomer. "I will not obey such orders," he answered calmly.

"That isn't enough." A pause. "Give me the controls to your main power drive. That should be enough to ensure nothing will happen to endanger the earth."

The computer considered for a moment. "Very well. Transferring all power flow to the auxiliary external maintenance cord."