My puppy suddenly foamed at the mouth and had seizures after a nap, and passed a dark brown stool while vomiting; then it kept barking, followed me around, and became listless, hiding in a corner to sleep.

Foaming at the mouth and seizures are mainly suggestive of abnormal neurological firing or nerve damage, so once the seizure eases, take your dog to a veterinary clinic for diagnosis and treatment promptly. If the seizure is caused by poisoning, get to the clinic as quickly as possible to identify the source and begin detoxification. Your dog’s symptoms are currently quite severe, and without timely treatment the condition could become life-threatening.