It is small, round and maroon or brown... one side has a 30 imprinted on it and the other side has a large M with a box around the letter...

You can look for this pill on the following web sites:

Pill Identifier - Drugs.com (http://www.drugs.com/pill_identification.html)
Common Imprints | Pharmer.org -- Pill Identification Resources (http://www.pharmer.org/imprints)

I would not want to be responsible for giving you information when I do not know who you are, where you found this pill, how you came to find this pill, and also why haven't you called either your pharmacy or your local emergency room or even law enfocement?