No it is not the end, I'll check back for you. Bur once you spoke to Dr Eilhart, you go to Dr Schmidt office (either the stranger guard the door for you, or there is a scene with Harold), you click on the clickable item (among which the flower pot), you get the key, you click on the cabinet, and the story continues
edit: alright so I checked, you have different possibilities. Once you have talked with Dr Eilhart you click on the left on "Doctor" to go to Dr Schmidt's office. A dialogue with the stranger pops. Either you accept his help, you enter the office, there is a couple of items you can click among which the flower pot. You get a key, after that you can click on a cabinet, the story continues. If you refuse the help from the stranger, you have to speak to Harold. Either you give him extra motivation, he lets you in, you click the flower pot, the cabinet and again the story goes on. If you talked to Harold but refuse the extra motivation, you have to click on the stranger, it automatically accept his help, he let you in, flower pot, cabinet, blablabla
