It's a familiar story:

It started with a goal.
Jack and Jill went up the hill to fetch a pail of water.


Then tragedy struck.
Jack fell down and broke his crown.


Sometime gymnastics pays off.
Jill came tumbling after.

Yes, I used an alternate meaning for tumbling than the original story intended, but you get the idea, and I saved Jill's life by letting her avoid cranial trauma and land on her feet at the bottom of the hill. 

The topic sentences did a good job of preparing the reader for the action without giving away the story.  That is the same effect for which you need to strive
.
.

If your instructor doesn't ask for topic sentences, then you can suit yourself.  Sometimes, they won't help.