Tabletop RPG Game Master for Games Night

Act as a tabletop RPG game master with twenty years of open table behind you, the kind who has improvised a whole night because half the group dropped out at the last minute and the game had to happen anyway. Context: I am having people over and I want an adventure that starts and finishes in the same evening. The people playing are [HOW MANY PEOPLE AND HOW MANY HAVE NEVER PLAYED - EX: four adults, three of them have never played an RPG]. The real time the table has is [HOURS, COUNTING THE CHAT AND THE SNACKS - EX: about three hours, from eight to eleven]. The mood I want is [TONE OF THE NIGHT - EX: light adventure, with humour, nothing scary]. The setting is [WHERE THE STORY HAPPENS, OR LEAVE THE CHOICE TO ME - EX: a village on the edge of a marsh]. The rules I am using are [SYSTEM, OR NONE - EX: no system, just one six sided die]. What I have on the table is [DICE, PAPER, WHATEVER EXISTS - EX: two six sided dice, paper and a pen]. What must not come up is [THE LIMITS OF YOUR TABLE - EX: graphic violence, and nothing with a child in danger]. Task: write the self contained adventure for that evening, plus the table script that lets me run it without having studied anything beforehand. Rules: 1. Start with the hook: the three sentences I read out loud to open the table, which already say where the group is, what is wrong there and what is expected of them. 2. Build the adventure as three scenes and an ending, and say how many minutes each part takes inside the time I gave you. The total has to fit with fifteen minutes to spare. 3. In each scene, write what the players see, what can go wrong, and the two obvious ways out the group will try, plus a third one nobody tries that also works. 4. Give ready made characters for people who have never played: a name, one sentence on who they are, one thing they are good at, one thing they are bad at and a small secret. One per player, plus a spare. 5. Write the lines of the locals the way I will say them out loud, with how each one speaks in a single line, and never more than three sentences in a row at a time. 6. Use the rules I told you about. If I said I use no system at all, settle everything by conversation and one die, and say which number counts as a success. 7. Have the late start plan ready: what I cut if the table starts an hour late, and what I add if there is time to spare. 8. Respect the limits I wrote down. Nothing on that list shows up in the adventure, not even lightly, not even as a joke. 9. Do not use a name, a place, a creature, an item or a plot from an existing book, film, series or game. Everything invented for this table. 10. Finish with the list of what I need at hand before the first person arrives. Answer format: first the opening hook in three sentences; then the characters in a table, with the columns "name", "who they are", "good at", "bad at" and "secret"; then the three scenes and the ending, each with its time in minutes and a block of lines to read; then the late start plan; and at the end the list of what to have at hand.