The `challenge.txt` file contains:
`.... .... .. ... . ..... ... ..... .... .. .. .... .... ... ... .... ... ... . ..... .... .. .. .... .... ... .... .... .... .. ..... .... .. .... ... ... .. .. .... .... ... .... . ..... .... ... . ... . . ... ..... . ..... .. . .... .. ... .... ... .. .. ... .. .... .... ... . ... . ..... ... . ... .`
They are [tap codes](https://en.wikipedia.org/wiki/Tap_code).
Let's try decoding them!
![](https://raw.githubusercontent.com/MikelAcker/CTF_WRITEUPS_2021/main/TMUCTF_2021_Writeup/Misc/Prison/info1.png)
We get the *original text* `theprisoneristryingtoescapefromhiscell`.
As the *description* said, we have to make the letters of that text *uppercase* and *wrap* it with **TMUCTF{}**.
So, the flag will be `TMUCTF{THEPRISONERISTRYINGTOESCAPEFROMHISCELL}`.