plaintiff, plaintive

Plaintiff or plaintiff means the party suing in a civil case--
The jury awarded a million dollars in damages to the plaintiff.
The judge decided that the plaintiff had brought a frivolous lawsuit to court.

Plaintive or plaintive means sad or mournful--
Our dog makes a plaintive wail every time he hears a siren.
The woman's plaintive cries commanded everyone's attention.

Now that you know that, you can say--
"The plaintive cries of the plaintiff could be heard through the entire building."

Note--in a civil suit, the plaintiff sues the defendant for loss or damages. In the United States, the plaintiff has to demonstrate financial loss, and sues for that amount. In a criminal case, the prosecution ( the state or government ) tries the defendant.