Searching for the true killer of Count Drebber, Sherlock and John set a trap for the culprit using a wedding ring found at the murder scene as bait. After a struggle in which the ring is lost, Sherlock is able to deduce who the real killer is.
Meaning that it's our one piece of evidence.
.ما يعني أنه جزء من الأدلة
Mit anderen Worten,
er ist das einzige Beweismittel.
Lo que significa
que es nuestra única evidencia.
Autrement dit, c’est notre seul indice.
Ou seja, é a nossa única evidência.
Это единственное
 вещественное доказательство.