What scene does Karim witness while cycling in Part One, Chapter Five?

Karim is cycling to clear his thoughts about how to help Jamila, when he sees Haroon acting strangely and using a pay phone. Haroon looks very happy while on the phone, then severely disappointed when he hangs up. Karim confronts Haroon, and Haroon admits that he loves Eva. Karim and Haroon both later pretend that the conversation never happened.