This mission will happen immediately after the Architect’s Plans mission.

Tracey will call asking for help with a stalker. You can choose to not help Tracey, but that will cost Michael $22,000.

If you choose to help, drive to Vinewood Plaza and meet her.

Once there, you will need to switch to her car.

Drive to the various places she mentions. Follow each way point until he's found.

Once he is found, kill or spare him.

Now drive Tracey home and the mission ends.