Intranet reachable wireless

Hi there,

I would need some help with my not yet "wireless network", please:

One laptop, where the ADSL coming in on USB is sending the stream via
NIC to the wireless router,
the second and the third connected wireless to the router can be seen
and accessed on the intranet.
The incoming laptop has the internet sharing enabled, and is the only
one which can access the internet.

The other can only access the files on the intranet-computers.

But as soon as I connect laptop two and three with cables on the
router, internet acces is no problem!

I don`t understand this logic. Please help!

Thanks in advance

Gerry