Castle Zadrian is a d20 System scenario for three to four 4th- to 5th-level characters. Part of AEG's Adventure Keep line of short, cheap modules in half-sized format (4-1/4"x11"), it is intended to be run as a single session. From the back cover:

When you read the posting for this job, you knew what you were getting yourself into.

"Lady of means requires assistance of a stalwart group of adventurers willing to undertake a mission of utmost importance. Discretion is required."

Words like that never mean that the woman in question is looking for someone to weed her garden — unless, of course, it's full of man-eating plants. Those are the words you only post if you're really in a bind. If it's a matter of life and death. If you're desperate for help and willing to pay for it through the nose.

It just so happens that you've made yourself quite a reputation lending just that kind of aid to people in just that kind of need. And the money hasn't hurt you any either. So when Lady Elena Zadrian tells you that her father — the near-legendary alchemist Sir Timoth Zadrian — has gone missing, well, you're not all that surprised.

Lady Elena looks up at you once again, brushing the long, blonde hair from her bright blue, tear-soaked eyes. "My father lives outside of a village only four day's ride from here, a sleepy, little place called Cuthder," she says. "He comes to see me every four months. He's a forgetful, old man, but I could set my clock by his visits." She chokes back a sob.

"It's been eight months since I saw him last. I fear something has gone horribly awry. Either brigands have robbed his tiny castle, or one of his experiments may have left him dead — or worse."

The lady stares you straight in the eye, and you can almost taste her desperation. "My father is a good man, wise and noble, but if word of this disappearance were to get out, it would hurl my household into a shambles. I need you to travel to his castle and learn for me what has happened to him, quickly and quietly.

"Please," she begs of you, her ruby-painted lower lip beginning to quiver. "I need your help. And I'm willing to pay — handsomely."

She has your attention.