It was no secret that Walter O'brien was protective of Ralph. The ten year old son of Paige, Scorpion's 'average intelligence' member, was a genius.

Walter didn't want Ralph to grow up like he, Toby, Sylvester, and Happy did. Isolated by his intelligence. That's probably why he was so put off by Paige bringing over a babysitter to watch Ralph rather than trusting the Scorpion team to watch him.

"I'm just saying," Walter told Paige, an uneasy edge in his voice. "You'd save time and money just letting us do it. We can work the case and watch Ralph."