Several minutes later, the Trackers stood outside Marvin Apartments staring at Dr. Newton’s message. Gabby squatted down and pointed at the lines. “This isn’t just a plus sign,” she said. “The lines are arrows. The top arrow points north, the next one points east, next comes south, and then this one is west. All the numbers are written between the south and west arrows. I think we should add up the numbers and walk that many steps southwest.”

“Very observant,” Pascal said.

“Let’s do the math,” Mr. C added.

The Trackers began adding the numbers together in chorus. “One hundred and ninety-six steps!” Gabby said. “We better hurry, or Dr. Newton will never make it to the dedication on time!”

‘Here,” Mr. C said, as he passed his watch to Gabby. “It has a compass on it.”

Gabby turned until she was facing southwest; then she led the Trackers across the lawn. They counted each step aloud and when they reached 196, they were facing the Physics Lecture Hall. The doors flew open and hundreds of students poured out so quickly the Trackers had no time to get out of the way. As they were surrounded by students, Gabby heard a student ask, “Hey, did anybody else see the numbers written on the side board? Who even uses the chalkboard anymore? And with purple chalk? What was that all about?”

Gabby grinned. This time, they were at the right place.