Someone gets a lawyer, and the parties attempt to work it out.
The summons must also be served per FRCP 4. That is, the defendant must be notified that a lawsuit has been started against her. Service can be effected personally, by mail, or through publication. Service can be a real hurdle to overcome if it's hard to locate the defendant. A motion to dismiss in effect admits the allegations in the complaint, but argues that even if the plaintiff could prove all those facts, he or she would still not be entitled to relief from the court.