Writing a one chapter murder mystery. Help me take up the challenge!

One of the POV characters of my book is themed on political intrigue and nostalgia. The second chapter has the general of the military and her husband, the president, sitting down with international ambassadors for dinner. The chapter ends when the president is poisoned and dies.

For the third chapter, I have the general holding the ambassadors hostage until they figure out who poisoned the president.

I've never written a murder mystery before, let alone one that I hope to resolve within a single chapter.

What should I consider including? I really like the setup I have, but I am unsure of how to make this intriguing.