Nina and the mysterious mailbox

Summary: A school election. A mysterious mailbox. And a letter from . . .Cleopatra? Middle school is so weird. Nina is determined to help her best friend Maya win the race for 6th grade representative. But when she uses her robotics skills to spy on Maya's opponent, the girls wind up in detention. There, they are asked to write a letter to a woman from history. Nina pours her heart out to Cleopatra, and instead of throwing the letter away so her parents don't find it, she slips it into a battered old mailbox she and Maya find in the woods. It was all just a game . . . until a giant scroll arrives at Nina's house, signed by Cleopatra herself! Do the girls really have a pen pal from 2,000 years ago? Will their friend Zoe ever speak to them again? Why is their science teacher acting so oddly? And what on Earth is a time taco?