  To investigate an effect of social interaction on the bystanders'
intervention in emergency situations we introduce a rescue model which includes
the effects of the victim's acquaintance with bystanders and those among
bystanders. This model reproduces the surprising experimental result that the
helping rate tends to decrease although the number of bystanders $k$ increases.
The model also shows that given the coupling effect among bystanders, for a
certain range of small $k$ the helping rate increases according to $k$ and that
coupling effect plays both positive and negative roles in emergencies. Finally
we find a broad range of coupling strength to maximize the helping rate.
