Yun Xi happened to need to get a pair of glasses, and then she encountered a "free clinic" held by a big hospital. As a poor student whose wallet was even emptier than her face by the end of each month, when coming across such a good thing that cost nothing, of course she would go there gladly.
However, when Yun Xi was trapped in the hospital area as if haunted by ghosts and saw the hospital management regulations in an instant, she painfully and remorsefully realized that something free was indeed the most expensive.
The free clinic in the hospital indeed didn't cost money, but it cost lives.