-To make something happens when a player enters an area you can choose between two different triggers. Trigger once will make something happens only once, that is, only the first time a player enters in the area. That?s useful for triggering an alarm sound, for example, the player enters, the alarm sounds.
Trigger multiple will allow you to make something happen each time the player enters in the area. Imagine you want an elevator to start working whenever the player is near it. Well, you set a trigger multiple there and each time the player approaches, the elevator is triggered.
There is not much science in making triggers work. Just set the name of the entity to be triggered in the TARGET field and we?re done. In the flags stuff you may find useful things. If you tick on "monsters", this entity can be activated by monsters. If you tick "Pushables" it can be activated by Func_pushable brushes and if you tick "No clients" the player won?t be able to trigger it. this may sound stupid but maybe you want something to happen when the scientist following you has passed through a point. Another value to take into consideration is the "Wait for retrigger" field: here you can set, in seconds, the time that a trigger multiple takes to be able of triggering something again. You may want a high value (for triggering along sound) or may want a short value (to trigger lights on and off).
-As for the moving scientist... Well, use a Scripted_sequence. A scripted sequence is an entity that makes someone do something, easy, ain?t it?. Youi can use to make the models play their animations, for moving them around... In fact, most of the complex actions that take place in Half Life are scripted sequences.
In your paritcular case, calculate a route for the movement in straight lines and set a scripted sequence in each one of the vertesex, incluiding the start and the end of the route. Name the first one and put in its target field the name of the second one. Name the second one and put in the target field the name of the third one... And so on. Dont?s set anything in the target field of the last point in the route because the movement is ending there. Name your monster and put its name in the "Monster Target" field of all the scripted sequences... Finally, in the "move to target" choose either walk or run (the one you want) and trigger the first scripted sequence with a trigger once, multiple, or whatever.
Hope this helps.