Eavesdropping

Have you ever eavesdropped on a conversation?  Sure you have.  Well...maybe you have.  I have.  Sometimes I heard something I really didn't need to know and sometimes I heard something that pleasantly surprised me and even came in handy. For instance, once I overheard a conversation about a volunteer opportunity that rrrreeeaaalllyyy interested me.  So, I signed up! Ha-ha!  What would it be like if someone eavesdropped on a conversation between two people about the Gospel?