Complex sentence: It was discovered that arsenic had been mixed with the materials of the dumplings, and suspicion alighting on Fenning she was summoned to Hatton Garden police-court, and was committed for trial.
Split into simpler sentences: It was discovered that arsenic had been mixed with the materials of the dumplings, and suspicion fell on Fenning. Fanning was summoned to Hatton Garden police-court, and was committed for trial.