The baby siamang thrived in the Hoffmanns’ care while they remained in the Sumatran jungle. Trouble did not arise until Unk was four months old and they returned home to Germany with a shipment of animals. At first, the trouble was nothing more than the Hoffmanns’ vague feeling that the little siamang was unhappy. Unk didn’t seem to enjoy his food as much as he once had, and he was eating less. He played less too, preferring to spend his time clinging to Gretchen. Finally, although he was kept warm and not taken outdoors in the chilly European winter, Unk caught cold and developed pneumonia.

Unk was a very sick little ape. Both a veterinarian and a pediatrician, who usually treated only human children, were called in. The two doctors prescribed medicine, but agreed that the case looked hopeless. Such a delicate young animal, so far from home and his own kind, would surely die.

The Hoffmanns refused to give up. For six long and terrible weeks, they stayed with Unk around the clock, sleeping in shifts. Their patient needed medicine every two hours, food to maintain his strength, warmth, and above all, love. The treatment worked. To the surprise of nearly everyone, especially the two doctors, and much to the relief of the Hoffmanns, Unk recovered completely.

Healthy once again, Unk behaved like a totally different ape. He was ten months old, and he quickly made up for lost growing time by developing a huge appetite. Not only did he finish his own meals in record time, he also helped Gretchen and Dieter finish theirs. He became an accomplished thief, sneaking up on the humans at the table, snatching a potato or a handful of string beans from a plate, and swinging away to a high shelf where no one could reach him. The Hoffmanns didn’t really mind, but their friends did. They soon found that no one would have supper at their house any more.

Unk loved to play. The Hoffmanns’ small house became a substitute jungle, and their furniture soon showed the effects of the siamang’s running, jumping, swinging, tearing, and biting. It seemed that he never became tired, and he hardly ever slept. Unk sat still only for grooming sessions, which he loved. He offered his long arms to Gretchen or Dieter for grooming, and in return, insisted on grooming his foster parents. He seemed confused by the lack of hair on their arms, but seemed to regard their abundant head hair as a special consolation prize. Each day he spent twenty minutes or more grooming Gretchen’s hair, using his fingers gently but deftly, and making soft murmuring noises of contentment all the while.
The Hoffmanns knew they would not be able to keep Unk forever. He was rapidly becoming too big and too strong to live free in their house. He was beginning to regard the house as the territory of his family, and beginning to defend it in normal siamang fashion. When anyone other that Gretchen or Dieter entered, he inflated his throat sac and gave loud calls of alarm. Not surprisingly, most visitors were alarmed, and so were the neighbors. And if an intruder was not scared away by the noise, Unk attacked with his teeth.