From The Gospel Project, is a great little video, only three minutes, which provides a short but able summary of the Old Testament.
I like resources like this for two reasons:
First, for most lay Christians, the stuff before Jesus is a bit of a blur of names, places, and dates, with no conceivable narrative unity.
Second, some lay Christians like to jump from Genesis 3 to Romans 5 and ignore the story of Israel and even minimize the Gospels as necessary parts of the divine plan for salvation.
Videos like this, even if I might say a few things different or emphasize other stuff, serve to overcome these problems.