There are other more direct instances in the show which show that it's Sam's body that leaps.
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The Color of Truth - The host is revealed in a later episode,
Shock Theater to walk with an arthritic limp however there is a behind the scenes tid bit (can't remember where I saw it, possibly the documentary on the first season DVD extras) that reveals that Don had told Scott upon inquiry
not to limp because he is physically Sam not Jesse Tyler.
The difference when he does in fact do the limp in
Shock Theater is that Sam actually believed he was Jesse Tyler.
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Blind Faith - his host is blind but he did not inherit that as is made perfectly clear in several instances. The most significant being when he nearly gets the famous host (falsely) exploited as a fraud by getting caught reading a dog food box.
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Nowhere to Run - The host has had both his legs amputated as a result of a war injury in Vietnam yet we clearly see Sam's in tact legs and at one point he is even able to stand when drastic measures are required to ensure the success of the leap.
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Trilogy Parts II and III - Sam conceives a daughter with the woman he leaped in to save that is determined by Ziggy to be Sam's own daughter not the host's. Her high IQ also clarifies that she has Sam's genes. If it weren't his body that leaps he would be incapable of passing on his own genes.
Personally I am not a fan of how several of the novels portray his soul leaping and how in turn this effects the condition of the waiting room visitor.
Loch Ness Leap in particular had a concept of the visitor that I found distasteful. I actually found a lot of that particular novel distasteful, but I am not a huge Sammy-Jo fan. So it's mostly a biased opinion.
Though I was pleasantly surprised in my re-reads by how many actually follow the show that it is his body.
You are not alone Michelle, most of the reviewers on Amazon were not pleased with
Heat Wave but while it had it's flaws such as Sam's playing his role too well, I happened to have enjoyed it (and I found the surprise appearance at the end delightful
). Those reviews had almost turned me off but you can't let the opinions of others steer you and I am glad I did not in this case. After how overdue I was to read it, I wasn't going to yield. See I had ordered a copy of it several years ago but had to request a refund as I never received it. I almost thought it was happening again as it took quite some time, as
Knights of the Morningstar is now. My best friend has already both obtained and read it and aside from a slow beginning she very much enjoyed it. It's one I never took an interest in before simply for the Knight theme but once I read the summery I realize I may still not have been then as it took until recently for the evil leapers to grow on me.