"I'd say 'use common sense', but I expect you know as well as I that sense is not actually all that common," she said. "Generally, I wouldn't worry too much about the odd butterfly, but killing is strongly discouraged. You'll be sent into the field with a stun weapon of some kind, and if you're careful, you might not even need that. Killing is the sort of thing that will get you disciplined, or expelled.

"It's extremely unlikely, however, that you'll blot yourself out." She smirked a little. "They try to send people to time-streams of sufficient degrees of difference to avoid that. As for creating alternate histories—" She frowned slightly, looking uncomfortable for the first time. "There's an argument that such things would come to pass regardless of our interference or lack thereof, that the creation of new branches of Time is simply the way the multiverse works. But there are as many theories as there are agents. To keep it simple—don't kill anyone and don't try to influence events while you're there. In other words, regardless of temptation or opportunity, don't go trying to assassinate Hitler."