Most good stories start with a fundamental list of ingredients: the initial situation, conflict, complication, climax, suspense, denouement, and conclusion. Great writers sometimes shake up the recipe and add some spice.
Initial Situation
Doctor Stockmann makes a discovery.
Everything looks hunky dory at the beginning of the play. Everyone expects the Baths to make the town lots of money. Out protagonist, Dr. Stockmann, is surrounded by friends and family who all seem to love him. There's definitely some sibling rivalry going on with his brother, the Mayor, but ultimately things look A-OK. Then the Doctor announces a little discovery: he's found out that the Baths are contaminated with bacteria. If something's not done, the water that is supposed to be healing people will make them sick instead. At the end of the act, the Doctor's supposed friends all congratulate him on his discovery and praise him as a hero.
Conflict
The Mayor brings bad news. The Doctor swears to persevere.
Both Aslaksen and Hovstad show up to promise the Doctor their support. At first the Doctor doesn't see what the big deal is. The water is poisoned. Everybody will want it fixed, right? Dr. Stockmann's bubble is quickly burst with the arrival of his brother, Mayor Stockmann. The Mayor tells Dr. Stockmann that it will ruin the town to fix the pollution in the Baths, and resorts to threatening his brother. The Doctor is undaunted by the Mayors threats and vows to make the truth known to all. By the end to the second act, the central conflict of the play is clear: Dr. Stockmann is going to struggle to bring out the truth no matter what the cost.
Complication
The Doctor is betrayed.
Act 3 starts off with the Doctor feeling confident of his success. He has the support of Aslaksen, the head of the Householders' Association, and Hovstad, the editor of the local newspaper has also promised support. Unfortunately, for the Doctor, his brother is far craftier than he thought. The Mayor cleverly turns Aslaksen and Hovstad against the Doctor by pointing out how much money it will cost to complete the proposed renovations. Before the Doctor knows what's happened, he's lost all his allies. His quest to reveal the truth has definitely gotten a lot more complicated.
Climax
The Doctor gives all of society a piece of his mind.
When The People's Herald refuses to publish his article about the pollution of the Baths, Dr. Stockmann calls a public meeting to read his discoveries out loud. Once again, though, he is foiled by his brother, who skillfully manipulates the rules of the meeting so as to not allow the Doctor to read his findings. Outraged, the Doctor rages about the corruption of society as a whole. The play reaches an emotional peak when Dr. Stockmann places the blame of all society's woes on the power of the ignorant majority, who keep freethinking, intelligent people like him from revealing the truth.
Suspense
The last temptations of Dr. Stockmann.
After the whole town riots against him, the Doctor is determined to leave them all behind a head to America. Several guests show up to tempt him before he makes his final decision. The Mayor, Aslaksen, Hovstad, and even his father-in-law, all come to try and manipulate him in some way.
Denouement
The Doctor refuses to abandon his quest.
Unfortunately for the Doctor's would-be tempters, their efforts only serve reignite Dr. Stockmann's passion. The Doctor swears stay in the town fight the good fight.
Conclusion
Dr. Stockmann vows to reeducate the world.
In the end, Dr. Stockmann decides that the only way to truly help society is through education. Along with his daughter Petra's help, he will take the poor children of the town and enlighten them. He hopes that by educating the young, he can fight the power of the complacent majority.