Although in a wired situation you can connect individual devices with a cross over network lead and get them to communicate. Once you add more devices using a hub you will not get any communication without a router.

In a WiFi network even with only two devices you need a router, hence why I said try and source a redundant modem since most supplied by ISPs have a router incorporated, that modem does not need to be linked to the Internet hence no need to connect to a phone socket. The only thing you have to provide is a mains supply, presumably you provide a mains supply for the laptop, just use a multi socket extension socket plug the modem/router into that or any convenient socket in the room.

Richard