Second Nancy Guthrie Demand Note, Last Chance To Pay For Kidnapper's Identity

TMZ has received another email from the person who claims to know the identity of Nancy Guthrie's kidnapper ... and the words are chilling.

As we reported, TMZ received an email Wednesday, asking for 1 bitcoin in return for the name of the kidnapper. A single bitcoin is currently worth around $65,000. We monitored the account all day, but nothing was deposited.

Just after 8 AM Pacific Time Thursday ... TMZ received a second email from the same person, who complained, "I am not being taken seriously." He makes some ominous statements in the email ... TMZ is cooperating with law enforcement by not disclosing specifics. One thing he makes clear ... the situation has changed from Wednesday to Thursday.

As for why he wants a bitcoin ... he says he will need money to lay low after identifying the kidnapper for fear of retaliation. He also worries he might be "incriminated like that Carlos [the deliveryman who was detained and released] guy."

He ends by saying this is his final attempt to help.

As of this post, no money or bitcoin has been deposited in his account.