Congratulations on having someone show interest in your invention idea.

However, by doing so without having protected yourself with either a prototype or a confidentiality agreement, you have left yourself vulnerable should this agent be less than honorable in his dealings with you.

It is very difficult to protect an idea, unless you've found a way to put it into a tangible form, such as with a patent, trademark or copyright. Speak to an intellectual property attorney about any steps that you can take to protect the idea at this point. They may also have insight into whether the company is legitimate and if the procedures they'll ask you to follow fit the norm.