Adapter is a wrapper that convert an interface to another interface. The common example of adapter I know is the adapter wrap only single object, but could it possible that adapter wrap more than one object?
A adapter pattern is not to wrap an interface! The Adapter pattern, as the name implies, adapts the interface of one class to match the interface expected by another class.
Typical usage is adapting a SQL interface to a ActiveRecord pattern.
In general you can adapt to multiple flavors of a Interface, by swapping to another adaper, based on a common class.