in chapter 18, what is the plan for Helmholtz and bernard?

The two men are leaving John to the experiment and returning home. This is the only mention of the men in Chapter Eightee. 

"Yes, we're off to-morrow," said Bernard on whose face the Savage remarked a new expression of determined resignation. "And by the way, John," he continued, leaning forward in his chair and laying a hand on the Savage's knee, "I want to say how sorry I am about everything that happened yesterday." He blushed. "How ashamed," he went on, in spite of the unsteadiness of his voice, "how really …"