Mills and Kneizys presented data in support of a light water “excess heat” reaction obtained with an electrolytic cell highly reminiscent of the Fleischmann-Pons “cold fusion” cell. The claim of Mills and Kneizys that their excess heat reaction can be explained on the basis of a novel chemistry, which supposedly also explains cold fusion, is rejected in favor of their reaction being, instead, a light water cold fusion reaction. If it is the first known light water cold fusion reaction to exhibit excess heat, it may serve as a prototype to expand our understanding of cold fusion. From this new hypothetical vantage point, a number of potential nuclear reactions are deduced, including those common to past cold fusion studies. This broader pattern of nuclear reactions is typically seen to involve a fusion of the nuclides of the alkali atoms with the simplest of the alkali-type nuclides, namely, protons, deuterons, and tritons. Thus, the term “alkali-hydrogen fusion” seems appropriate for this new type of reaction with three subclasses: alkali-hydrogen fusion, alkali-deuterium fusion, and alkali-tritium fusion. A significant part of the difference between alkali-hydrogen fusion and thermonuclear fusion is hypothesized to involve an effect that is essentially the opposite of the well-known Mössbauer effect. Transfer of energy to the lattice is shown to be consistent with the uncertainty principle and special relativity. The implications of alkali-hydrogen fusion for theoretical models for cold fusion are considered. Boson properties are suggested to be unimportant for alkali-hydrogen fusion, which apparently rules out the prospect that a Bose-Einstein condensation could be involved in cold fusion. A new three-dimensional transmission resonance model (TRM) is sketched that avoids Jände's criticism of the one-dimensional TRM. When the new TRM is coupled with the alkali-hydrogen fusion hypothesis for cold fusion, it suggests a solution for the surface, or near-surface, excess heat effect for cold fusion in the form of a reaction between 6Li and a deuteron to produce 4He, or between two deuterons to produce predominantly 4He. A lattice effect essentially opposite to an “umklapp” process suggests that energy should be given to the lattice in the reaction. Finally, preliminary experimental evidence in support of the hypothesis o f a light water nuclear reaction and alkali-hydrogen fusion is reported. Excess heat has been detected with light water-based electrolytes for the separate cases of K2CO3, Na2CO3, Rb2CO3, and RbOH. Preliminary evidence for a correlation between the amount of elemental strontium produced in the case of Rb2CO3 as the electrolyte, or of elemental calcium produced in the case of K2CO3 as the electrolyte, and the total excess heats produced in the respective cells has been mixed. Evidence is presented that appears to strongly implicate the transmission resonance phenomenon of the new TRM.