One of his friends rushed inside to call an ambulance, then he phoned Tracy's father,
Bill Marsh. Bill raced to the hospital, where he was joined by Tracy's mother, Cory.
She knew from the way the doctors talked that there was little hope.
be joined by什么意思?与...会合吗?怎么用被动语态?
个人理解此处应该就是汇合的意思,用被动语态我想是因为where引导的只是一个非限定定语从句,对hospital做补充说明作用,为了保持和主句的主语一致,从句用了he做主语,而Bill是先到的,Cory是后到的,只能是Cory加入Bill,所以采用了被动语态。