What does "wrung out of promise" mean?

Question

could you, please, help me to understand the meaning of "wrung out of promise" in this sentence? Does it mean, that investigation of every possible version led police to nowhere?

Only once before has she worked on anything like this – a girl called Bryony Taylor, snatched on her way home from school in Yeovil, a town just beyond the Dorset border. Avon and Somerset Police led that investigation, with Mairéad drafted in to offer support. A year later, the case is still active, but every line of enquiry feels like it’s been wrung dry of promise. Sam Lloyd "The Memory Wood"

Thanks!

Answer 1

Collins Dictionary suggests the following definition for wring out:

When you wring out a wet cloth or a wet piece of clothing, you squeeze the water out of it by twisting it strongly.

And the image below shows how this might look.

Figuratively, if a line of enquiry feels like it’s been wrung dry of promise, then it contains no more promise, no more hope. The investigators feel that they will be unable to solve the crime.