Dear Prof. Wang,

 

　　I’m writing to ask you to excuse me for not being able to keep our appointment. I do know that this is very impolite and must have caused you much trouble.

 

　　I do reckon that at present any explanation is pale and futile. However I do not want you to misunderstand me. On my way to your office, an old lady suddenly fainted due to heart attack on the bus. I stopped a taxi and sent her into a nearby hospital. I stayed there until her son came, which spoiled our appointment.

 

　　I am aware that our appointment is of importance. I do hope that you would be kind enough to spare your valuable to meet me.

 

　　I am looking forward to hearing from you.

 

　　Sincerely Yours