1998 Nissan Frontier CAR WON'T START

Hi - my son's Nissan has been stored for one year - he wants to drive it again now but it wouldn't start. He thought it was the battery so we had AAA come and install a new battery but it still won't start; the AAA guy said he thinks the problem is that the factory installed alarm is preventing it from starting. He (my son) says that there is a red wire hanging loose in the engine that he thinks needs to be connected inside the truck, but he's not sure.

Any advice?

Thanks